A specialized VM opcode for the array_key_exists()
    function has been added, which improves performance of this function
    if it can be statically resolved. In namespaced code, this may require
    writing \array_key_exists() or explicitly importing
    the function.
   
    When preg_match() in UTF-8 mode ("u" modifier)
    is repeatedly called on the same string (but possibly different offsets),
    it will only be checked for UTF-8 validity once.
   
zend.exception_ignore_args is a new INI directive for including or excluding arguments from stack traces generated from exceptions.
opcache.preload_user is a new INI directive for specifying the user account under which preloading code is execute if it would otherwise be run as root (which is not allowed for security reasons).
   A number of extensions have been migrated to exclusively use pkg-config for the
   detection of library dependencies. Generally, this means that instead of using
   --with-foo-dir=DIR or similar only
   --with-foo is used. Custom library paths can be
   specified either by adding additional directories to PKG_CONFIG_PATH
   or by explicitly specifying compilation options through FOO_CFLAGS
   and FOO_LIBS.
  
The following extensions and SAPIs are affected:
   fputcsv(),
   fgetcsv(),
   SplFileObject::fputcsv(), 
   SplFileObject::fgetcsv(), and
   SplFileObject::setCsvControl()
   now accept an empty string as $escape argument,
   which disables the proprietary PHP escaping mechanism.
  
The behavior of str_getcsv() has been adjusted accordingly (formerly, an empty string was identical to using the default).
SplFileObject::getCsvControl() now may also return an empty string for the third array element, accordingly.
The filter extension no longer exposes --with-pcre-dir for Unix builds and can now reliably be built as shared when using ./configure
The behavior of imagecropauto() in the bundled libgd has been synced with that of system libgd:
IMG_CROP_DEFAULT is no longer falling
     back to IMG_CROP_SIDES
    
   
   The default $mode parameter of
   imagecropauto() has been changed to
   IMG_CROP_DEFAULT; passing -1
   is now deprecated.
  
   imagescale() now supports aspect ratio preserving
   scaling to a fixed height by passing -1
   as $new_width.
  
The hash extension cannot be disabled anymore and is always an integral part of any PHP build, similar to the date extension.
Support for nsldap and umich_ldap has been removed.
All libxml-based extensions now require libxml 2.7.6 or newer.
The oniguruma library is no longer bundled with PHP, instead libonig needs to be available on the system. Alternatively --disable-mbregex can be used to disable the mbregex component.
The --disable-opcache-file and --enable-opcache-file configure options have been removed in favor of the opcache.file_cache INI directive.
   The password_hash() and
   password_needs_rehash() functions
   now accept nullable string and int for $algo argument.
  
Installation of PEAR (including PECL) is no longer enabled by default. It can be explicitly enabled using --with-pear. This option is deprecated and may be removed in the future.
   The numeric values of the modifier constants
   (IS_ABSTRACT,
   IS_DEPRECATED,
   IS_EXPLICIT_ABSTRACT,
   IS_FINAL,
   IS_IMPLICIT_ABSTRACT,
   IS_PRIVATE,
   IS_PROTECTED,
   IS_PUBLIC, and
   IS_STATIC) on the
   ReflectionClass,
   ReflectionFunction,
   ReflectionMethod,
   ReflectionObject, and
   ReflectionProperty
   classes have changed.
  
SimpleXMLElement now implements Countable.
The bundled libsqlite has been removed. To build the SQLite3 extension a system libsqlite3 ≥ 3.7.4 is now required. To build the PDO_SQLite extension a system libsqlite3 ≥ 3.5.0 is now required.
Serialization and unserialization of SQLite3, SQLite3Stmt and SQLite3Result is now explicitly forbidden. Formerly, serialization of instances of these classes was possible, but unserialization yielded unusable objects.
   The @param notation can now also be used to
   denote SQL query parameters.
  
The bundled libzip library has been removed. A system libzip >= 0.11 is now necessary to build the zip extension.