Description:
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---
From manual page: http://www.php.net/function.array-shift#refsect1-function.array-shift-seealso
---

Having an associative array where the keys are number-strings (enclosed in quotes as strings - see example), this strings get converted into numbers when using array_shift().

This is a severe bug! 

Test script:
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$a["_"] = "blank dummy";
$a["01"] = "one";
$a["10"] = "ten";
$a["20"] = "twenty";

print_r( $a );
echo $a["10"] . "\n";

array_shift( $a );

print_r( $a );
echo $a["10"] . "\n"; // THIS PRODUCES AN UNDEFINED INDEX ERROR
echo $a["20"] . "\n"; // THIS PRODUCES AN UNDEFINED INDEX ERROR

echo $a[0] . "\n"; // THIS SHOULD PRODUCE AN ERROR BUT SHOWS THE VALUE
echo $a[1] . "\n"; // THIS SHOULD PRODUCE AN ERROR BUT SHOWS THE VALUE

Expected result:
----------------
I expect that the line 

echo $a["10"] . "\n";

will produce "ten" as an output, also echo $a["20"] . "\n"; should output "twenty".

Actual result:
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Notice:  Undefined index: 10 in [test] on line 13