Stupid PHP Tricks

PHP is an incredibly flexible language, with an interesting array of built-in functionality. In this talk, I’ll show you some of my favorite and hidden features in PHP. Learn how to abuse output buffering, the [] operator, and three ways to limit how long a function can execute.

Presented on November 14, 2014 at php[world].

Transcript

1. © 2014 John Bafford php[world] 2014 — 11/14/2014
   “Stupid PHP Tricks”
   John Bafford!
   http://bafford.com — @jbafford — john@bafford.com
   !
   The Brick Factory!
   http://thebrickfactory.com — @thebrickfactory — jbafford@thebrickfactory.com
   1
   

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2. © 2014 John Bafford php[world] 2014 — 11/13/2014
   Who Am I?
   • John Bafford

   Vice President, Programming Services

   The Brick Factory
   • PHP developer since 1999
   • Programmer since 1990
   2
   

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3. © 2014 John Bafford php[world] 2014 — 11/13/2014
   The Brick Factory
   • Full Service Web Development Shop
   • Farragut North, DC
   • We do lots of Drupal sites
   3
   

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4. © 2014 John Bafford php[world] 2014 — 11/13/2014
   Output Buffers
   4
   

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5. © 2014 John Bafford php[world] 2014 — 11/13/2014
   Pop Quiz
   function a(){ echo 'Hello'; echo 'World'; }
   function b(){ echo 'Hello', 'World'; }
   function c(){ echo 'Hello' . 'World'; }
   5
   

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6. function a(){ echo 'Hello'; echo 'World'; }
   !
   line # * op fetch ext return operands!
   ---------------------------------------------------------------------------------!
   3 0 > ECHO 'Hello'!
   1 ECHO 'World'!
   2 > RETURN null!
   !
   !
   !
   function b(){ echo 'Hello', 'World'; }
   !
   line # * op fetch ext return operands!
   ---------------------------------------------------------------------------------!
   4 0 > ECHO 'Hello'!
   1 ECHO 'World'!
   2 > RETURN null!
   !
   !
   !
   function c(){ echo 'Hello' . 'World'; }
   !
   line # * op fetch ext return operands!
   ---------------------------------------------------------------------------------!
   5 0 > CONCAT ~0 'Hello', 'World'!
   1 ECHO ~0!
   2 > RETURN null!
   

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7. function a(){ echo 'Hello'; echo 'World'; }
   !
   line # * op fetch ext return operands!
   ---------------------------------------------------------------------------------!
   3 0 > ECHO 'Hello'!
   1 ECHO 'World'!
   2 > RETURN null!
   !
   !
   !
   function b(){ echo 'Hello', 'World'; }
   !
   line # * op fetch ext return operands!
   ---------------------------------------------------------------------------------!
   4 0 > ECHO 'Hello'!
   1 ECHO 'World'!
   2 > RETURN null!
   !
   !
   !
   function c(){ echo 'Hello' . 'World'; }
   !
   line # * op fetch ext return operands!
   ---------------------------------------------------------------------------------!
   5 0 > CONCAT ~0 'Hello', 'World'!
   1 ECHO ~0!
   2 > RETURN null!
   

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8. function a(){ echo 'Hello'; echo 'World'; }
   function b(){ echo 'Hello', 'World'; }
   function c(){ echo 'Hello' . 'World'; }
   function obwrap($fn)
   {
   ob_start(function($s) { return $s . $s; }, 1);
   $fn();
   ob_end_clean();
   }
   $ob = false;
   for($x = 1; $x < $argc; $x++) {
   $fn = $argv[$x];
   if($fn == ‘--ob') {
   $ob = true;
   continue;
   }
   echo "$fn:\n";
   if($ob)
   obwrap($fn);
   else
   $fn();
   echo "\n\n";
   }
   php st-ob.php a b c!
   a:!
   HelloWorld!
   !
   b:!
   HelloWorld!
   !
   c:!
   HelloWorld!
   

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9. function a(){ echo 'Hello'; echo 'World'; }
   function b(){ echo 'Hello', 'World'; }
   function c(){ echo 'Hello' . 'World'; }
   function obwrap($fn)
   {
   ob_start(function($s) { return $s . $s; }, 1);
   $fn();
   ob_end_clean();
   }
   $ob = false;
   for($x = 1; $x < $argc; $x++) {
   $fn = $argv[$x];
   if($fn == ‘--ob') {
   $ob = true;
   continue;
   }
   echo "$fn:\n";
   if($ob)
   obwrap($fn);
   else
   $fn();
   echo "\n\n";
   }
   php st-ob.php a b c!
   a:!
   HelloWorld!
   !
   b:!
   HelloWorld!
   !
   c:!
   HelloWorld!
   php st-ob.php --ob a b c!
   a:!
   HelloHelloWorldWorld!
   !
   b:!
   HelloHelloWorldWorld!
   !
   c:!
   HelloWorldHelloWorld!
   

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10. php st-ob.php --ob a b c!
    a:!
    HelloHelloWorldWorld!
    !
    b:!
    HelloHelloWorldWorld!
    !
    c:!
    HelloWorldHelloWorld!
    

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11. chunk_size
    
    If the optional parameter chunk_size is passed, the buffer will be flushed after any output call
    which causes the buffer's length to equal or exceed chunk_size. The default value 0 means that
    the output function will only be called when the output buffer is closed.
    
    !
    Prior to PHP 5.4.0, the value 1 was a special case value that set the chunk size to 4096 bytes.
    
    bool ob_start (
    
    
    
    
    
    
    
    [ callable $output_callback = NULL
    
    
    
    
    
    
    
    [, int $chunk_size = 0
    
    
    
    
    
    
    
    [, int $flags = PHP_OUTPUT_HANDLER_STDFLAGS
    
    
    
    
    
    
    ]]] )
    

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12. function a(){ echo 'Hello'; echo 'World'; }
    function b(){ echo 'Hello', 'World'; }
    function c(){ echo 'Hello' . 'World'; }
    function obwrap($fn)
    {
    ob_start(function($s) { return $s . $s; }, 1);
    $fn();
    ob_end_clean();
    }
    $ob = false;
    for($x = 1; $x < $argc; $x++) {
    $fn = $argv[$x];
    if($fn == ‘--ob') {
    $ob = true;
    continue;
    }
    echo "$fn:\n";
    if($ob)
    obwrap($fn);
    else
    $fn();
    echo "\n\n";
    }
    php st-ob.php a b c!
    a:!
    HelloWorld!
    !
    b:!
    HelloWorld!
    !
    c:!
    HelloWorld!
    php st-ob.php --ob a b c!
    a:!
    HelloHelloWorldWorld!
    !
    b:!
    HelloHelloWorldWorld!
    !
    c:!
    HelloWorldHelloWorld!
    

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13. © 2014 John Bafford php[world] 2014 — 11/13/2014
    http_build_query
    13
    

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14. Generates a URL-encoded query string from the associative (or indexed) array provided.
    string http_build_query (
    
    
    mixed $query_data
    
    
    [, string $numeric_prefix
    
    
    [, string $arg_separator
    
    
    [, int $enc_type = PHP_QUERY_RFC1738
    
    ]]] )
    

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15. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Please Don’t Write This
    $url = "https://your.favorite.api/favoritizer/
    json?api_key=%s&api_secret=
    %s&param_one=value&param_two=%s&%message=%s";
    $encoded = urlencode($some_message)
    $url = sprintf($url, $api_key, $api_secret,
    'value', $param_two, $encoded);
    15
    

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16. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Write This Instead
    $url = "https://your.favorite.api/favoritizer/
    json?" . http_build_query([
    'api_key' => $api_key,
    'api_secret' => $api_secret,
    'param_one' => 'value',
    'param_two' => $param_two,
    'message' => $some_message,
    ]);
    16
    

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17. © 2014 John Bafford php[world] 2014 — 11/13/2014
    []
    17
    

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18. $array = [];
    $array[] = 'foo';
    $array[] = 'bar';
    print_r($array);
    /*
    Array
    (
    [0] => foo
    [1] => bar
    )
    */
    

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19. $array = [];
    $array[] = 'foo';
    $array[] = 'bar';
    print_r($array);
    /*
    Array
    (
    [0] => foo
    [1] => bar
    )
    */
    !
    !
    $x = $array[];
    /*
    Fatal error: Cannot use [] for reading in …/phpworld/StupidPHPTricks/array.php on line
    124
    */
    

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20. $array = [];
    $array[] = 'foo';
    $array[] = 'bar';
    print_r($array);
    /*
    Array
    (
    [0] => foo
    [1] => bar
    )
    */
    !
    !
    $foo = 'foo';
    $bar = &$foo;
    var_dump($foo, $bar);
    /*
    string(3) "foo"
    string(3) "foo"
    */
    !
    !
    !
    $bar = 'bar';
    var_dump($foo, $bar);
    /*
    string(3) "bar"
    string(3) "bar"
    */
    

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21. $array = [];
    $array[] = 'foo';
    $array[] = 'bar';
    print_r($array);
    /*
    Array
    (
    [0] => foo
    [1] => bar
    )
    */
    $array[] = &$foo;
    $foo = 'baz';
    print_r($array);
    /*
    Array
    (
    [0] => foo
    [1] => bar
    [2] => baz
    )
    */
    

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22. $array = [];
    $array[] = 'foo';
    $array[] = 'bar';
    !
    !
    $baz = ['foo', 'bar'];
    $array[] = &$baz;
    $baz[] = 'baz';
    print_r($array);
    /*
    Array
    (
    [0] => foo
    [1] => bar
    [2] => Array
    (
    [0] => foo
    [1] => bar
    [2] => baz
    )
    )
    */
    

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23. function setGreek(&$output)
    {
    $output = ['α', 'β', 'ɣ', 'δ'];
    }
    !
    $x = null;
    setGreek($x);
    print_r($x);
    !
    /*
    Array
    (
    [0] => α
    [1] => β
    [2] => ɣ
    [3] => δ
    )
    */
    

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24. function setGreek(&$output)
    {
    $output = ['α', 'β', 'ɣ', 'δ'];
    }
    !
    !
    setGreek($x);
    print_r($x);
    !
    /*
    Array
    (
    [0] => α
    [1] => β
    [2] => ɣ
    [3] => δ
    )
    */
    

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25. function setGreek(&$output)
    {
    $output = ['α', 'β', 'ɣ', 'δ'];
    }
    !
    $values = [
    ['1', '2', '3'],
    ['a', 'b', 'c'],
    ];
    !
    setGreek($values[]);
    print_r($values);
    /*
    Array
    (
    [0] => Array
    (
    [0] => 1
    [1] => 2
    [2] => 3
    )
    [1] => Array
    (
    [0] => a
    [1] => b
    [2] => c
    )
    [2] => Array
    (
    [0] => α
    [1] => β
    [2] => ɣ
    [3] => δ
    )
    )
    */
    

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26. $a = [1, 2, 3];
    $b = &$a[];
    $c = &$a[];
    $a[] = 'a';
    $b = 'b';
    $c = 'c';
    print_r($a);
    /*
    Array
    (
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => b
    [4] => c
    [5] => a
    )
    */
    

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27. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Practical Application of
    &$arr[]
    27
    

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28. $xml = simplexml_load_string(file_get_contents('xml.xml'));
    $array = json_decode(json_encode((array) $xml), true);
    $array = array($xml->getName() => $array);
    

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29. function _parse($xml) {
    $_level = array();
    $_cdata = '';
    $_data = array();
    while($xml->read()) {
    switch($xml->nodeType) {
    case XMLReader::ELEMENT:
    $_cdata = '';
    $name = $xml->name;
    $curLevel = count($_level);
    if($curLevel == 0) //the root
    $_level[] = &$_data[$name][];
    else
    $_level[] = &$_level[$curLevel - 1][$name][];
    //Fall-through and close the tag if it is empty
    if(!$xml->isEmptyElement)
    break;
    case XMLReader::END_ELEMENT:
    if($_cdata != '')
    {
    $curLevel = count($_level) - 1;
    $_level[$curLevel] = $_cdata;
    $_cdata = '';
    }
    array_pop($_level);
    break;
    case XMLReader::TEXT:
    case XMLReader::CDATA:
    $_cdata .= $xml->value;
    break;
    }
    }
    return $_data;
    }
    

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30. 
    
    one
    two
    three
    four
    
    Array(!
    [foo] => Array(!
    [0] => Array(!
    [bar] => Array(!
    [0] => one!
    [1] => two!
    )!
    !
    [baz] => Array(!
    [0] => three!
    [1] => Array(!
    [quux] => Array(!
    [0] => four!
    )!
    )!
    )!
    )!
    )!
    )
    

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31. © 2014 John Bafford php[world] 2014 — 11/13/2014
    array_combine
    31
    

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32. Creates an array by using the values from the keys array as keys
    and the values from the values array as the corresponding values.
    array array_combine ( array $keys , array $values )
    

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33. © 2014 John Bafford php[world] 2014 — 11/13/2014
    array_combine
    $fd = fopen('somefile.csv', 'r');
    $cols = null;
    while(false !== ($row = fgetcsv($fd)))
    {
    if(!$cols)
    $cols = $row;
    else if(count($row) == count($cols))
    {
    $row = array_combine($cols, $row);
    print_r($row);
    }
    }
    33
    A,B,C!
    1,2,3!
    4,5,6
    Array!
    (!
    [A] => 1!
    [B] => 2!
    [C] => 3!
    )!
    Array!
    (!
    [A] => 4!
    [B] => 5!
    [C] => 6!
    )!
    

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34. © 2014 John Bafford php[world] 2014 — 11/13/2014
    (unset)
    34
    

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35. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Unset cast
    • Returns null
    • That’s it.
    35
    

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36. $foo = 'foo';
    $bar = (unset)$foo;
    $foo === 'foo';
    $bar === null;
    

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37. © 2014 John Bafford php[world] 2014 — 11/13/2014
    WHY??
    37
    

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38. $bar = (
    $foo
    ? FuncA()
    : (unset)FuncB()
    );
    

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39. $bar = (
    $foo
    ? FuncA()
    : (unset)FuncB()
    );
    if($foo) {
    $bar = FuncA();
    } else {
    FuncB();
    $bar = null;
    }
    

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40. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Controlling Runaway
    Functions
    40
    

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41. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Controlling Runaway Functions
    • PHP has limited multithreading support
    • There’s the pthreads pecl module, but it’s unlikely you
    have --enable-maintainer-zts enabled
    41
    

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42. A tick is an event that occurs for every N low-level tickable statements
    executed by the parser within the declare block. The value for N is
    specified using ticks=N within the declare block's directive section.
    declare(ticks = 1);
    

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43. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Method 1
    SIGALRM
    43
    

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44. class LimitExecutionAlarm {
    function __construct($time, $fn) {
    $this->limit = $time;
    $this->fn = $fn;
    }
    function run() {
    pcntl_signal(SIGALRM, function() {
    echo “HALT!\n";
    exit;
    });
    pcntl_alarm($this->limit);
    $fn = $this->fn;
    $fn();
    echo "Stopped.\n";
    }
    }
    function slowFunc()
    {
    for($x = 0;; $x++)
    {
    echo "Iteration $x\n";
    sleep(1);
    }
    }
    $slow = new LimitExecutionAlarm(

    10,
    ‘slowFunc'
    );
    $slow->run();
    

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45. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Method 2
    Modify the Original Function
    45
    

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46. class LimitExecutionThrottleable {
    function __construct($time, $fn) {
    $this->limit = $time;
    $this->fn = $fn;
    }
    function run() {
    $halt = false;
    pcntl_signal(SIGALRM,
    function() use(&$halt) {
    $halt = true;
    });
    pcntl_alarm($this->limit);
    $fn = $this->fn;
    $fn($halt);
    echo "Stopped.\n";
    }
    }
    function slowFuncThrottleable(&$halt = false)
    {
    for($x = 0;; $x++)
    {
    echo "Iteration $x\n";
    sleep(1);
    if($halt)
    {
    echo "halt requested\n";
    break;
    }
    }
    }
    $slow = new LimitExecutionThrottleable(
    10,
    ‘slowFuncThrottleable'
    );
    $slow->run();
    

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47. © 2014 John Bafford php[world] 2014 — 11/13/2014
    Method 3
    fork
    47
    

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48. class LimitExecutionFork {
    function run() {
    $pid = pcntl_fork();
    if($pid == -1) { //error
    } else if($pid) { //parent
    echo "Forked $pid\n";
    $done = false;
    pcntl_signal(SIGALRM,
    function() use($pid) {
    if(!$done) {
    posix_kill($pid, SIGTERM);
    echo "Killed $pid.\n”;
    }
    });
    pcntl_alarm($this->limit);
    $status = false;
    $child = pcntl_wait($status);
    $done = true;
    } else { //child
    $fn = $this->fn;
    $fn();
    exit;
    }
    }
    }
    function slowFunc()
    {
    for($x = 0;; $x++)
    {
    echo "Iteration $x\n";
    sleep(1);
    }
    }
    $slow = new LimitExecutionFork(
    10,
    ‘slowFunc'
    );
    $slow->run();
    

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49. © 2014 John Bafford php[world] 2014 — 11/14/2014
    https://joind.in/talk/view/11915
    !
    John Bafford!
    http://bafford.com — @jbafford — john@bafford.com
    !
    The Brick Factory!
    http://thebrickfactory.com — @thebrickfactory — jbafford@thebrickfactory.com
    Questions?
    49
    

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50. © 2014 John Bafford php[world] 2014 — 11/14/2014
    https://joind.in/talk/view/11915
    !
    John Bafford!
    http://bafford.com — @jbafford — john@bafford.com
    !
    The Brick Factory!
    http://thebrickfactory.com — @thebrickfactory — jbafford@thebrickfactory.com
    Thank You!
    50
    

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