When preg_split's argc is only 1, like preg_split("/foo/"),
reproduce crash.
The cause of this problem is to forget the check of argc==1
in ext/pcre/php_pcre.c line 1070.

  1068 /* Get function parameters and do error checking */
  1069 argc = ZEND_NUM_ARGS();
  1070 if (argc < 1 || argc > 4 ||
zend_get_parameters_ex(argc, &regex, &subject, &limit,
&flags) == FAILURE) {
  1071        WRONG_PARAM_COUNT;
  1072 }

Thus this should be
  1070 if (argc < 2 || argc >4 || ...

This problem reason is very clear, so I don't attach gdb
backtrace. Thank you.