sb@wopr-mobile ~ % cat test.php
<?php
?>
sb@wopr-mobile ~ % gdb php
GNU gdb 6.3
Copyright 2004 Free Software Foundation, Inc.
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This GDB was configured as "i686-pc-linux-gnu"...Using host libthread_db library "/lib/tls/libthread_db.so.1".

(gdb) r test.php
Starting program: /usr/local/php-5.1/bin/php test.php
[Thread debugging using libthread_db enabled]
[New Thread -1211069792 (LWP 23840)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1211069792 (LWP 23840)]
0xb7cecc83 in add_stack_frame (zdata=0x0, op_array=0x845debc, type=0)
at /home/sb/xdebug/xdebug.c:906
906 if (XDEBUG_LLIST_TAIL(XG(stack))) {
(gdb) bt
#0 0xb7cecc83 in add_stack_frame (zdata=0x0, op_array=0x845debc, type=0)
at /home/sb/xdebug/xdebug.c:906
#1 0xb7cedcc1 in xdebug_execute (op_array=0x845debc)
at /home/sb/xdebug/xdebug.c:1123
0000002 0x08279696 in zend_execute_scripts (type=8, retval=0x0, file_count=3)
at /usr/local/src/php/php-5.1/Zend/zend.c:1087
0000003 0x0822ffcd in php_execute_script (primary_file=0xbffeefb0)
at /usr/local/src/php/php-5.1/main/main.c:1671
0000004 0x082f04b3 in main (argc=2, argv=0xbffef084)
at /usr/local/src/php/php-5.1/sapi/cli/php_cli.c:1039