Migrating from PHP 7.1.x to PHP 7.2.x
PHP Manual

Backward incompatible changes

Prevent number_format() from returning negative zero

Previously, it was possible for the number_format() function to return -0. Whilst this is perfectly valid according to the IEEE 754 floating point specification, this oddity was not desirable for displaying formatted numbers in a human-readable form.

<?php

var_dump
(number_format(-0.01)); // now outputs string(1) "0" instead of string(2) "-0"

Convert numeric keys in object and array casts

Numeric keys are now better handled when casting arrays to object and objects to arrays (either from explicit casting or by settype()).

This means that integer (or stringy integer) keys from arrays being casted to objects are now accessible:

<?php

// array to object
$arr = [=> 1];
$obj = (object)$arr;
var_dump(
    
$obj,
    
$obj->{'0'}, // now accessible
    
$obj->{0// now accessible
);

The above example will output:

object(stdClass)#1 (1) {
  ["0"]=>    // string key now, rather than integer key
  int(1)
}
int(1)
int(1)

And integer (or stringy integer) keys from objects being casted to arrays are now accessible:

<?php

// object to array
$obj = new class {
    public function 
__construct()
    {
        
$this->{0} = 1;
    }
};
$arr = (array)$obj;
var_dump(
    
$arr,
    
$arr[0], // now accessible
    
$arr['0'// now accessible
);

The above example will output:

array(1) {
  [0]=>    // integer key now, rather than string key
  int(1)
}
int(1)
int(1)

Disallow Passing NULL to get_class()

Previously, passing NULL to the get_class() function would output the name of the enclosing class. This behaviour has now been removed, where an E_WARNING will be output instead. To achieve the same behaviour as before, the argument should simply be omitted instead.

Warn when counting non-countable types

An E_WARNING will now be emitted when attempting to count() non-countable types (this includes the sizeof() alias function).

<?php

var_dump
(
    
count(1), // integers are not countable
    
count('abc'), // strings are not countable
    
count(new stdclass), // objects not implementing the Countable interface are not countable
    
count([1,2]) // arrays are countable
);

The above example will output:

Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d

Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d

Warning: count(): Parameter must be an array or an object that implements Countable in %s on line %d
int(1)
int(1)
int(1)
int(2)

Move ext/hash from resources to objects

As part of the long-term migration away from resources, the Hash extension has been updated to use objects instead of resources. The change should be seamless for PHP developers, except for where is_resource() checks have been made (which will need updating to is_object() instead).

Improve SSL/TLS Defaults

The following changes to the defaults have been made:


Migrating from PHP 7.1.x to PHP 7.2.x
PHP Manual