The array itself wasn't passed by reference to the function, so PHP knows that it isn't allowed to modify the outside array, so it therefore makes a copy of the array's internal iteration offset state (that's just a simple number which says which item you are currently at during things like foreach()), which costs almost no performance or memory at all since it's just a small number. The array function argument itself isn't passed by reference, so the function knows it isn't allowed to modify the original at all. This function takes an array as argument ($arr).
Lots of people think the answer is two() because it uses "reference to value, which it doesn't have to copy each value when it loops". WARNING: Looping through "values by reference" for "extra performance" is an old myth.
#Foreach php key value archive#
To prevent this behavior it is sufficient to add an unset($value) statement after each loop where it is used.Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Errors Exceptions Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto search
More info here: PHP: Passing by Reference
#Foreach php key value code#
It's very confusing, but it's not even slightly idiosyncratic it's the code executing exactly as it should. So in the 3rd iteration of the second loop, $value and $variable become equal to 4 by reference, then during the 4th and final iteration of the second loop, nothing changes because you're passing the value of $variable (which is still &$value) to $value (which is still &$value). With each evaluation of this foreach, both $value and $variable are becoming equal to the value of the iterable item in $variable. At the end of the first loop, $value is pointing to the same place as $variable ( they are pointing to the same location in memory): $variable = Įven as this loop is finished, $value is still a reference that's pointing to the same location in memory as $variable, so each time you store a value in $value, this also overwrites the value stored for $variable: foreach ($variable as $key => $value)
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