1.2.947. PHP5 Indirect Variable Expression

Indirect variable expressions changes between PHP 5 an 7.

The following structures are evaluated differently in PHP 5 and 7. It is recommended to review them or switch to a less ambiguous syntax. +———————–+————————-+————————-+ | Expression | PHP 5 interpretation | PHP 7 interpretation | +———————–+————————-+————————-+ |$$foo[‘bar’][‘baz’] |${$foo[‘bar’][‘baz’]} |($$foo)[‘bar’][‘baz’] | |$foo->$bar[‘baz’] |$foo->{$bar[‘baz’]} |($foo->$bar)[‘baz’] | |$foo->$bar[‘baz’]() |$foo->{$bar[‘baz’]}() |($foo->$bar)[‘baz’]() | |Foo::$bar[‘baz’]() |Foo::{$bar[‘baz’]}() |(Foo::$bar)[‘baz’]() | +———————–+————————-+————————-+

<?php

// PHP 7
$foo = 'bar';
$bar['bar']['baz'] = 'foobarbarbaz';
echo $$foo['bar']['baz'];
echo ($$foo)['bar']['baz'];

// PHP 5
$foo['bar']['baz'] = 'bar';
$bar = 'foobarbazbar';
echo $$foo['bar']['baz'];
echo $\{$foo['bar']['baz']\};

?>

See also Backward incompatible changes PHP 7.0.

1.2.947.1. Suggestions

• Avoid using complex expressions, mixing $$\, [0] and -> in the same expression

• Add curly braces {} to ensure that the precedence is the same between PHP 5 and 7. For example, $$v becomes $\{$v\}

1.2.947.2. Specs

Short name	Variables/Php5IndirectExpression
Rulesets	All, CompatibilityPHP53, CompatibilityPHP54, CompatibilityPHP55, CompatibilityPHP56
Exakat since	0.8.4
PHP Version	With PHP 7.0 and older
Severity	Major
Time To Fix	Slow (1 hour)
Precision	Very high
Features	global
Available in	Entreprise Edition, Exakat Cloud