What’s New in PHP 7.3?

iscountable rfc
PHP 7.2 added a warning when counting uncountable objects. The iscountable function can help prevent this warning.

$count = iscountable($variable) ? count($variable) : null;
arraykeyfirst and arraykey_last rfc
These two functions basically do what the name says.

$array = [
'a' => '…',
'b' => '…',
'c' => '…',
];

arraykeyfirst($array); // 'a'
arraykeylast($array); // 'c'
The original RFC also proposed arrayvaluefirst and arrayvaluelast, but these were voted against by the majority of people.

Another idea for arrayfirst and arraylast was proposed which would return a tuple [$key => $value], but opinions were mixed. For now we only have two functions to get the first and last key of an array.

Flexible Heredoc syntax rfc
Heredoc can be a useful tool for larger strings, though they had a indentation quirck in the past.

// Instead of this:

$query = <<<SQL
SELECT *
FROM table
WHERE column = true;
SQL;

// You can do this:

$query = <<<SQL
SELECT *
FROM table
WHERE column = true;
SQL;
This is especially useful when you're using Heredoc in an already nested context.

The whitespaces in front of the closing marker will be ignored on all lines.

An important note: because of this change, some existing Heredocs might break, when they are using the same closing marker in their body.

$str = <<<FOO
abcdefg
FOO
FOO;

// Parse error: Invalid body indentation level in PHP 7.3
Tailing commas in function calls rfc
What was already possible with arrays, can now also be done with function calls. Note that it's not possible in function definitions!

$compacted = compact(
'posts',
'units',
);
Better type error reporting
TypeErrors for integers and booleans used to print out that full name, it has been changed to int and bool, to match the type hints in the code.

Argument 1 passed to foo() must be of the type int/bool
In comparison to PHP 7.2:

Argument 1 passed to foo() must be of the type
integer/boolean
JSON errors can be thrown rfc
Previously, JSON parse errors were a hassle to debug. The JSON functions now accept an extra option to make them throw an exception on parsing errors. This change obviously adds a new exception: JsonException.

jsonencode($data, JSONTHROWONERROR);

jsondecode("invalid json", null, 512, JSONTHROWONERROR);

// Throws JsonException
While this feature is only available with the newly added option, there's a chance it'll be the default behaviour in a future version.

list reference assignment rfc
The list() and its shorthand [] syntax now support references.

$array = [1, 2];

list($a, &$b) = $array;

$b = 3;

// $array = [1, 3];
Undefined variables in compact rfc
Undefined variables passed to compact will be reported with a notice, they were previously ignored.

$a = 'foo';

compact('a', 'b');

// Notice: compact(): Undefined variable: b
Case-insensitive constants rfc
There were a few edge cases were case-insensitive constants were allowed. These have been deprecated.

Same site cookie rfc
This change not only adds a new parameter, it also changes to way the setcookie, setrawcookie and sessionsetcookie_params functions work in a non-breaking manner.

Instead of one more parameter added to already huge functions, they now support an array of options, whilst still being backwards compatible. An example:

bool setcookie(
string $name
[, string $value = ""
[, int $expire = 0
[, string $path = ""
[, string $domain = ""
[, bool $secure = false
[, bool $httponly = false ]]]]]]
)

bool setcookie (
string $name
[, string $value = ""
[, int $expire = 0
[, array $options ]]]
)

// Both ways work.
Several deprecations rfc
Several small things have been deprecated, there's a possibility errors can show up in your code because of this.

Undocumented mbstring function aliases
String search functions with integer needle
fgetss() function and string.striptags filter
Defining a free-standing assert() function
FILTERFLAGSCHEMEREQUIRED and FILTERFLAGHOSTREQUIRED flags
pdoodbc.db2instancename php.ini directive