Although most existing PHP 5 code should work without changes, please take note of some backward incompatible changes:
Previously, arrays declared as class properties which mixed explicit and implicit keys could have array elements silently overwritten if an explicit key was the same as a sequential implicit key. For example:
<?php
class C {
const ONE = 1;
public $array = [
self::ONE => 'foo',
'bar',
'quux',
];
}
var_dump((new C)->array);
?>Output of the above example in PHP 5.5:
array(2) {
[0]=>
string(3) "bar"
[1]=>
string(4) "quux"
}
Output of the above example in PHP 5.6:
array(3) {
[1]=>
string(3) "foo"
[2]=>
string(3) "bar"
[3]=>
string(4) "quux"
}
json_decode() now rejects non-lowercase variants of the
JSON literals true, false and
null at all times, as per the JSON specification, and
sets json_last_error() accordingly. Previously, inputs
to json_decode() that consisted solely of one of these
values in upper or mixed case were accepted.
This change will only affect cases where invalid JSON was being passed to json_decode(): valid JSON input is unaffected and will continue to be parsed normally.
All encrypted client streams now enable peer verification by default. By default, this will use OpenSSL's default CA bundle to verify the peer certificate. In most cases, no changes will need to be made to communicate with servers with valid SSL certificates, as distributors generally configure OpenSSL to use known good CA bundles.
The default CA bundle may be overridden on a global basis by setting
either the openssl.cafile or openssl.capath configuration setting, or on a
per request basis by using the
cafile or
capath
context options.
While not recommended in general, it is possible to disable peer
certificate verification for a request by setting the
verify_peer
context option to false, and to disable peer name validation by setting
the verify_peer_name
context option to false.
GMP resources are now objects. The functional API implemented in the GMP extension has not changed, and code should run unmodified unless it checks explicitly for a resource using is_resource() or similar.
mcrypt_encrypt(), mcrypt_decrypt(), mcrypt_cbc(), mcrypt_cfb(), mcrypt_ecb(), mcrypt_generic() and mcrypt_ofb() will no longer accept keys or IVs with incorrect sizes, and block cipher modes that require IVs will now fail if an IV isn't provided.