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run code in 200+ php & hhvm versions
Bugs & Features
<?php // from http://stackoverflow.com/a/3764809/4251625 function refcount($var) { ob_start(); debug_zval_dump($var); $dump = ob_get_clean(); $matches = array(); preg_match('/refcount\(([0-9]+)/', $dump, $matches); $count = $matches[1]; //3 references are added, including when calling debug_zval_dump() return $count - 3; } class SomethingBuilder { protected $value; protected $listeners = []; protected function dispatchEvent($evt){ foreach($this->listeners as $listener) $listener($evt); } function addEventListener($listener){ $this->listeners[] = $listener; } function getValue(){ return $this->value; } function setValue($value){ $this->dispatchEvent('beforechange'); $this->value = $value; } function freeze(){ return new SomethingFinalBuilderWrapper($this); } } class SomethingFinalBuilderWrapper { protected $builder; function __construct(SomethingBuilder $builder){ $this->builder = $builder; $this->builder->addEventListener(function($evt){ if($evt !== 'beforechange') return; echo refcount($this->builder); // if(refcount($this->builder) > 1) $this->builder = clone $this->builder; echo "clone happened\n"; }); } function getValue(){ return $this->builder->getValue(); } } $x = new SomethingBuilder(); $x->setValue(10); echo $x->getValue() . "\n"; $y = $x->freeze(); $x->setValue(20); echo $y->getValue() . "\n"; echo $x->getValue() . "\n"; $y = $x->freeze(); $z = $x->freeze(); $x->setValue(20); echo $y->getValue() . "\n"; echo $x->getValue() . "\n";
Output for 7.0.0 - 7.2.6
10 2clone happened 10 20 0clone happened 3clone happened 2clone happened 20 20
Output for 5.4.0 - 5.6.28
10 4clone happened 10 20 1clone happened 5clone happened 4clone happened 20 20
Output for 5.1.0 - 5.3.29
Parse error: syntax error, unexpected '[' in /in/0942s on line 22
Process exited with code 255.
Output for 5.0.0 - 5.0.5
Parse error: parse error, unexpected '[' in /in/0942s on line 22
Process exited with code 255.
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /in/0942s on line 21
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.4.1
Parse error: parse error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /in/0942s on line 21
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `T_OLD_FUNCTION' or `T_FUNCTION' or `T_VAR' or `'}'' in /in/0942s on line 21
Process exited with code 255.