includes/ScopedPHPTimeout.php

   1 <?php
   2
   3 /**
   4  * Class to expand PHP execution time for a function call.
   5  * On construction, set_time_limit() is called and set to $seconds.
   6  * When the object goes out of scope, the timer is restarted, with
   7  * the original time limit minus the time the object existed.
   8  */
   9 class ScopedPHPTimeout {
  10         protected $startTime; // float; seconds
  11         protected $oldTimeout; // integer; seconds
  12
  13         protected static $stackDepth = 0; // integer
  14         protected static $totalCalls = 0; // integer
  15         protected static $totalElapsed = 0; // float; seconds
  16
  17         /* Prevent callers in infinite loops from running forever */
  18         const MAX_TOTAL_CALLS = 1000000;
  19         const MAX_TOTAL_TIME = 300; // seconds
  20
  21         /**
  22          * @param $seconds integer
  23          */
  24         public function __construct( $seconds ) {
  25                 if ( ini_get( 'max_execution_time' ) > 0 ) { // CLI uses 0
  26                         if ( self::$totalCalls >= self::MAX_TOTAL_CALLS ) {
  27                                 trigger_error( "Maximum invocations of " . __CLASS__ . " exceeded." );
  28                         } elseif ( self::$totalElapsed >= self::MAX_TOTAL_TIME ) {
  29                                 trigger_error( "Time limit within invocations of " . __CLASS__ . " exceeded." );
  30                         } elseif ( self::$stackDepth > 0 ) { // recursion guard
  31                                 trigger_error( "Resursive invocation of " . __CLASS__ . " attempted." );
  32                         } else {
  33                                 $this->oldTimeout = ini_set( 'max_execution_time', $seconds );
  34                                 $this->startTime = microtime( true );
  35                                 ++self::$stackDepth;
  36                                 ++self::$totalCalls; // proof against < 1us scopes
  37                         }
  38                 }
  39         }
  40
  41         /**
  42          * Restore the original timeout.
  43          * This does not account for the timer value on __construct().
  44          */
  45         public function __destruct() {
  46                 if ( $this->oldTimeout ) {
  47                         $elapsed = microtime( true ) - $this->startTime;
  48                         // Note: a limit of 0 is treated as "forever"
  49                         set_time_limit( max( 1, $this->oldTimeout - (int)$elapsed ) );
  50                         // If each scoped timeout is for less than one second, we end up
  51                         // restoring the original timeout without any decrease in value.
  52                         // Thus web scripts in an infinite loop can run forever unless we
  53                         // take some measures to prevent this. Track total time and calls.
  54                         self::$totalElapsed += $elapsed;
  55                         --self::$stackDepth;
  56                 }
  57         }
  58 }