Are PHP Integer array Indexes really numeric?

According to the documentation, one of "the […] key casts [that] will occur" is:

Strings containing valid integers will be cast to the integer type. E.g. the key "8" will actually be stored under 8. On the other hand "08" will not be cast, as it isn't a valid decimal integer.

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Q1. Because 00 = 0 numerically

Q2. Because the index is "00" not 00

Try:

$test=array(00=>"A","B","C","D","E");print_r($test);/*Array(    [0] => A    [1] => B    [2] => C    [3] => D    [4] => E)*/

Q3.

echo gettype("00");# stringecho gettype(00);# integerecho gettype("0");# stringecho gettype(0);# integer

From the manual:http://php.net/manual/en/language.types.array.php

Strings containing valid integers will be cast to the integer type. E.g. the key "8" will actually be stored under 8. On the other hand "08" will not be cast, as it isn't a valid decimal integer.

Edited after comment

Q4. I think OP's question is essentially why the second and the forth behave differently:

php > var_dump("00" === 0);bool(false)php > var_dump(00 === 0);bool(true)php > var_dump("08" === 8);bool(false)php > var_dump(08 === 8);bool(false)

I have no answer yet.

"anystring" == 0; //true"0000" == 0;      //true"0" == 0;      //true