ScopedPHPTimeout.php

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<?php
class ScopedPHPTimeout {
    protected $startTime; // float; seconds
    protected $oldTimeout; // integer; seconds
    protected $oldIgnoreAbort; // boolean

    protected static $stackDepth = 0; // integer
    protected static $totalCalls = 0; // integer
    protected static $totalElapsed = 0; // float; seconds

    /* Prevent callers in infinite loops from running forever */
    const MAX_TOTAL_CALLS = 1000000;
    const MAX_TOTAL_TIME = 300; // seconds

    public function __construct( $seconds ) {
        if ( ini_get( 'max_execution_time' ) > 0 ) { // CLI uses 0
            if ( self::$totalCalls >= self::MAX_TOTAL_CALLS ) {
                trigger_error( "Maximum invocations of " . __CLASS__ . " exceeded." );
            } elseif ( self::$totalElapsed >= self::MAX_TOTAL_TIME ) {
                trigger_error( "Time limit within invocations of " . __CLASS__ . " exceeded." );
            } elseif ( self::$stackDepth > 0 ) { // recursion guard
                trigger_error( "Resursive invocation of " . __CLASS__ . " attempted." );
            } else {
                $this->oldIgnoreAbort = ignore_user_abort( true );
                $this->oldTimeout = ini_set( 'max_execution_time', $seconds );
                $this->startTime = microtime( true );
                ++self::$stackDepth;
                ++self::$totalCalls; // proof against < 1us scopes
            }
        }
    }

    public function __destruct() {
        if ( $this->oldTimeout ) {
            $elapsed = microtime( true ) - $this->startTime;
            // Note: a limit of 0 is treated as "forever"
            set_time_limit( max( 1, $this->oldTimeout - (int)$elapsed ) );
            // If each scoped timeout is for less than one second, we end up
            // restoring the original timeout without any decrease in value.
            // Thus web scripts in an infinite loop can run forever unless we
            // take some measures to prevent this. Track total time and calls.
            self::$totalElapsed += $elapsed;
            --self::$stackDepth;
            ignore_user_abort( $this->oldIgnoreAbort );
        }
    }
}