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Dave at SymmetricDesigns dot com ¶

16 years ago

Another example of something to watch out for when using references with arrays.  It seems that even an usused reference to an array cell modifies the *source* of the reference.  Strange behavior for an assignment statement (is this why I've seen it written as an =& operator?  - although this doesn't happen with regular variables).
<?php
    $array1 = array(1,2);
    $x = &$array1[1];   // Unused reference
    $array2 = $array1;  // reference now also applies to $array2 !
    $array2[1]=22;      // (changing [0] will not affect $array1)
    print_r($array1);
?>
Produces:
    Array
    (
    [0] => 1
    [1] => 22    // var_dump() will show the & here
    )

I fixed my bug by rewriting the code without references, but it can also be fixed with the unset() function:
<?php
    $array1 = array(1,2);
    $x = &$array1[1];
    $array2 = $array1;
    unset($x); // Array copy is now unaffected by above reference
    $array2[1]=22;
    print_r($array1);
?>
Produces:
    Array
    (
    [0] => 1
    [1] => 2
    )

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