Description:
------------
The script

<?php
$sh = new SessionHandler;
session_set_save_handler($sh);

$savePath = ini_get('session.save_path');
$sessionName = ini_get('session.name');

// session_start(); // Uncommenting this makes it not crash when reading the session (see below), but it will not return any data. 

$sh->open($savePath, $sessionName);
$sh->write("foo", "bar");
$sh->read($id);

Results in a crash (running with -n). Backtrace:

Program received signal SIGSEGV, Segmentation fault.
__strcmp_ssse3 () at ../sysdeps/i386/i686/multiarch/strcmp-ssse3.S:233
233	../sysdeps/i386/i686/multiarch/strcmp-ssse3.S: No such file or directory.
(gdb) bt
#0  __strcmp_ssse3 () at ../sysdeps/i386/i686/multiarch/strcmp-ssse3.S:233
#1  0x082ba633 in ps_files_open (data=0xb7fbfa58, key=0x0, tsrm_ls=0x894bd80)
    at /home/nikic/dev/php-5.5/ext/session/mod_files.c:127
#2  0x082bb146 in ps_read_files (mod_data=0x89eea24, key=0xb7fc0e7c "", 
    val=0xbfffbc9c, vallen=0xbfffbca4, tsrm_ls=0x894bd80)
    at /home/nikic/dev/php-5.5/ext/session/mod_files.c:362
#3  0x082acca3 in zim_SessionHandler_read (ht=1, return_value=0xb7fc0eb0, 
    return_value_ptr=0x0, this_ptr=0xb7fbdf48, return_value_used=0, 
    tsrm_ls=0x894bd80)
    at /home/nikic/dev/php-5.5/ext/session/mod_user_class.c:83
#4  0x08486b53 in zend_do_fcall_common_helper_SPEC (execute_data=0xb7fa216c, 
    tsrm_ls=0x894bd80) at /home/nikic/dev/php-5.5/Zend/zend_vm_execute.h:550
#5  0x084873e4 in ZEND_DO_FCALL_BY_NAME_SPEC_HANDLER (execute_data=0xb7fa216c, 
    tsrm_ls=0x894bd80) at /home/nikic/dev/php-5.5/Zend/zend_vm_execute.h:685
#6  0x084860ff in execute_ex (execute_data=0xb7fa216c, tsrm_ls=0x894bd80)
    at /home/nikic/dev/php-5.5/Zend/zend_vm_execute.h:363
#7  0x084861b4 in zend_execute (op_array=0xb7fbe7f4, tsrm_ls=0x894bd80)
    at /home/nikic/dev/php-5.5/Zend/zend_vm_execute.h:388
#8  0x0844ad81 in zend_execute_scripts (type=8, tsrm_ls=0x894bd80, retval=0x0, 
    file_count=3) at /home/nikic/dev/php-5.5/Zend/zend.c:1327
#9  0x083ad5f2 in php_execute_script (primary_file=0xbfffe0f0, 
    tsrm_ls=0x894bd80) at /home/nikic/dev/php-5.5/main/main.c:2506
#10 0x084f4783 in do_cli (argc=2, argv=0x894bce8, tsrm_ls=0x894bd80)

The issue is that PS(id) is NULL in the following line:

(gdb) f 2
#2  0x082bb146 in ps_read_files (mod_data=0x89eea24, key=0xb7fc0e7c "", 
    val=0xbfffbc9c, vallen=0xbfffbca4, tsrm_ls=0x894bd80)
    at /home/nikic/dev/php-5.5/ext/session/mod_files.c:362
362		ps_files_open(data, PS(id) TSRMLS_CC);

This is a regression from https://github.com/php/php-src/commit/16411586449c7562b840d6226f6ef55f567c35f3 which fixed bug #65475.