Deprecated features in PHP 7.2.x

Unquoted strings
Unquoted strings that are non-existent global constants are taken to be strings of themselves. This behaviour used to emit an 
E_NOTICE, but will now emit an 
E_WARNING. In the next major version of PHP, an 
Error exception will be thrown instead.
<?php
var_dump(NONEXISTENT);
/* Output:
Warning: Use of undefined constant NONEXISTENT - assumed 'NONEXISTENT' (this will throw an Error in a future version of PHP) in %s on line %d
string(11) "NONEXISTENT"
*/
   
png2wbmp and 
jpeg2wbmp
The 
png2wbmp and 
jpeg2wbmp functions from the GD extension have now been deprecated and will be removed in the next major version of PHP.
INTL_IDNA_VARIANT_2003 variant
The Intl extension has deprecated the 
INTL_IDNA_VARIANT_2003 variant, which is currently being used as the default for 
idn_to_ascii and 
idn_to_utf8. PHP 7.4 will see these defaults changed to 
INTL_IDNA_VARIANT_UTS46, and the next major version of PHP will remove 
INTL_IDNA_VARIANT_2003 altogether.
__autoload method
The 
__autoload method has been deprecated because it is inferior to 
spl_autoload_register (due to it not being able to chain autoloaders), and there is no interoperability between the two autoloading styles.
track_errors ini setting and 
$php_errormsg variable
When the 
track_errors ini setting is enabled, a 
$php_errormsg variable is created in the local scope when a non-fatal error occurs. Given that the preferred way of retrieving such error information is by using 
error_get_last, this feature has been deprecated.
create_function function
Given the security issues of this function (being a thin wrapper around 
eval), this dated function has now been deprecated. The preferred alternative is to use anonymous functions.
mbstring.func_overload ini setting
Given the interoperability problems of string-based functions being used in environments with this setting enabled, it has now been deprecated.
(unset) cast
Casting any expression to this type will always result in ENTITY, and so this superfluous casting type has now been deprecated.
parse_str without a second argument
Without the second argument to 
parse_str, the query string parameters would populate the local symbol table. Given the security implications of this, using 
parse_str without a second argument has now been deprecated. The function should always be used with two arguments, as the second argument causes the query string to be parsed into an array.
gmp_random function
This function generates a random number based upon a range that is calculated by an unexposed, platform-specific limb size. Because of this, the function has now been deprecated. The preferred way of generating a random number using the GMP extension is by 
gmp_random_bits and 
gmp_random_range.
each function
This function is far slower at iteration than a normal 
foreach, and causes implementation issues for some language changes. It has therefore been deprecated.
assert with a string argument
Using 
assert with a string argument required the string to be 
eval'ed. Given the potential for remote code execution, using 
assert with a string argument has now been deprecated in favour of using boolean expressions.
$errcontext argument of error handlers
The 
$errcontext argument contains all local variables of the error site. Given its rare usage, and the problems it causes with internal optimisations, it has now been deprecated. Instead, a debugger should be used to retrieve information on local variables at the error site.
read_exif_data function
The 
read_exif_data alias has been deprecated. The 
exif_read_data function should be used instead.