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rfc:calltimebyref [2008/05/21 13:08] – sfox | rfc:calltimebyref [2009/02/19 17:44] – Clarification sfox |
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This RFC aims to clarify the situation with call-time pass-by-ref in PHP 5.3. | This RFC aims to clarify the situation with call-time pass-by-ref in PHP 5.3. |
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Before PHP 4.0 was released, ''allow_call_time_pass_reference'' was introduced as a means of retaining back compatibility with PHP 3, at the point where returning by reference from a function declaration became possible [1]. By default, the INI switch has been On since inception [2]. The warning (formerly ''E_COMPILE_WARNING'' but currently ''E_DEPRECATED'') is only thrown if the INI switch is Off. You therefore need to **explicitly** switch off the directive in order to discover that the behaviour is deprecated. | Before PHP 4.0 was released, ''allow_call_time_pass_reference'' was introduced as a means of retaining back compatibility with PHP 3, at the point where returning by reference from a function declaration became possible [1]. By default, the INI switch has been On since inception [2]. The warning (formerly ''E_COMPILE_WARNING'' but currently ''E_DEPRECATED'') is only thrown if the INI switch is Off. You therefore need to **explicitly** switch off the directive in order to discover that the behaviour is deprecated. |
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At the time ''allow_call_time_pass_reference'' was introduced, php.ini-recommended was interestingly referred to as 'php.ini-optimized'. Over the years, it has become fairly standard to regard php.ini-recommended as 'production settings'; things like ''display_errors=Off'' and ''log_errors=On'' have helped this perception along. For the last 8 years, therefore, the first anyone is likely to have known about their code being less than kosher is when it went live. | At the time ''allow_call_time_pass_reference'' was introduced, php.ini-recommended was interestingly referred to as 'php.ini-optimized'. Over the years, it has become fairly standard to regard php.ini-recommended as 'production settings'; things like ''display_errors=Off'' and ''log_errors=On'' have helped this perception along. From inception, ''allow_call_time_pass_reference'' was switched ''Off'' in php.ini-recommended but ''On'' in php.ini-dist and by default. For the last 8 years, therefore, the first anyone is likely to have known about their code being less than kosher is when it went live. |
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Even in the current php.ini-recommended, the switch is attributed only to 'Code cleanliness'. The full entry in the heading about changed settings reads: | Even in the current php.ini-recommended, the switch is attributed only to 'Code cleanliness'. The full entry in the heading about changed settings reads: |
</code> | </code> |
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In fact, allowing return values by reference is the default behaviour in PHP, and has been from PHP 4.0 beta right up to PHP 5.3. | In fact, allowing values to be passed by reference is the default behaviour in PHP, and has been from PHP 4.0 beta right up to PHP 5.3. |
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===== Reality Check ===== | ===== Reality Check ===== |
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In some circumstances, on some platforms, returning values by reference can actually speed up your code. In most cases, though - and for all when it comes to large arrays - it carries a performance penalty. If you make use of by-ref for performance reasons on a given platform, that optimization will not be portable. | In some circumstances, on some platforms, passing values by reference can actually speed up your code. In most cases, though - and for all when it comes to large arrays - it carries a performance penalty. If you make use of by-ref for performance reasons on a given platform, that optimization will not be portable. |
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===== Future ===== | ===== Future ===== |
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The directive is completely gone from CVS HEAD [3]. The effect of this originally was that a new-to-many ''E_STRICT'' would be thrown when values are returned by reference. However, it's been moved to ''E_DEPRECATED'' recently. In either case, it will no longer be possible to turn the warning off. | The directive is completely gone from CVS HEAD [3]. The effect of this originally was that a new-to-many ''E_STRICT'' would be thrown when values are passed by reference. However, it's been moved to ''E_DEPRECATED'' recently. In either case, it will no longer be possible to turn the warning off. |
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===== Proposal ===== | ===== Proposal ===== |