Description:
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The JSON standard allows positive numbers to be represented with an explicit "+" sign, e.g. +123 (see the "sign" production on https://www.json.org/json-en.html). json_decode() fails and returns NULL for any JSON string that contains such a number.

Also affects 7.3 and 7.4 branches.

Test script:
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<?php

$x=json_decode('+123.4');
var_export($x);
print("\n");

$x=json_decode('123.4');
var_export($x);
print("\n");


Expected result:
----------------
123.4
123.4


Actual result:
--------------
NULL
123.4