PHP extract() Function

The PHP extract() function imports variables from an array into the current symbol table. It converts array keys into variable names and array values into variable values. For each key/value pair it creates a variable in the current symbol table, subject to flags and prefix parameters.

This function checks each key to see whether it has a valid variable name. It also checks for collisions with existing variables in the symbol table.

Syntax

extract(array, flags, prefix)

Parameters

`array`	`Required.` Specify an array to use. It must be an associative array. A numerically indexed array will not produce results unless EXTR_PREFIX_ALL or EXTR_PREFIX_INVALID parameter is used.
`flags`	`Optional.` Specify the way invalid/numeric keys and collisions are treated is determined by the extraction flags. It can be one of the following values: EXTR_OVERWRITE - (Default) On collision, overwrite the existing variable. EXTR_SKIP - On collision, don't overwrite the existing variable. EXTR_PREFIX_SAME - On collision, prefix the variable name with prefix. EXTR_PREFIX_ALL - Prefix all variable names with prefix. EXTR_PREFIX_INVALID - Only prefix invalid/numeric variable names with prefix. EXTR_IF_EXISTS - Only overwrite the variable if it already exists in the current symbol table, otherwise do nothing. EXTR_PREFIX_IF_EXISTS - Only add prefix to variable names if the non-prefixed version of the same variable exists in the current symbol table. EXTR_REFS - Extracts variables as references. The imported variables are still referencing the values of the array parameter. This flag can be combined with any other flag by OR'ing the flags.
`prefix`	`Optional.` Specify prefix. It is only required if flags is EXTR_PREFIX_SAME, EXTR_PREFIX_ALL, EXTR_PREFIX_INVALID or EXTR_PREFIX_IF_EXISTS. If the prefixed result is not a valid variable name, it is not imported into the symbol table. Prefixes are automatically separated from the array key by an underscore character.

Return Value

Returns the number of variables successfully imported into the symbol table.

Example: extract() example

The example below shows the usage of extract() function.

<?php
//the input array
$arr = array("color" => "red",
             "size"  => 10,
             "shape" => "cube");

extract($arr);


//after using extract() function
echo "\$color = $color \n";
echo "\$size = $size \n";
echo "\$shape = $shape \n";
?>

The output of the above code will be:

$color = red 
$size = 10 
$shape = cube

Example: handling collision

In the example below, there is a collision due to $color variable. But this variable is not overwritten because the EXTR_PREFIX_SAME flag is used which resulted in $new_color variable being created.

<?php
$color = "black";

//the input array
$arr = array("color" => "red",
             "size"  => 10,
             "shape" => "cube");

extract($arr, EXTR_PREFIX_SAME, "new");


//after using extract() function
echo "\$color = $color \n";
echo "\$size = $size \n";
echo "\$shape = $shape \n";
echo "\$new_color = $new_color \n";
?>

The output of the above code will be:

$color = black 
$size = 10 
$shape = cube 
$new_color = red

❮ PHP Array Reference