(gdb) bt
#0 0x00007fffecaed4a7 in xdebug_header_handler (h=0x7fffffffdae0, s=0x1, tsrm_ls=0x7d1dc0) at /usr/src/debug/xdebug-2.1/xdebug.c:2579
#1 0x00007ffff33a4134 in sapi_header_op (op=SAPI_HEADER_ADD, arg=<value optimized out>, tsrm_ls=0x7d1c20) at /usr/src/debug/php5.3-200905091830/main/SAPI.c:758
0000002 0x00007ffff33a478b in sapi_add_header_ex (header_line=0xacc200 "Content-type: text/html", header_line_len=<value optimized out>, duplicate=<value optimized out>, replace=176 '\260', tsrm_ls=0x6c6d74682f7478)
at /usr/src/debug/php5.3-200905091830/main/SAPI.c:518
0000003 0x00007ffff33a52ba in sapi_send_headers (tsrm_ls=0x7d1c20) at /usr/src/debug/php5.3-200905091830/main/SAPI.c:828
0000004 0x00007ffff3339b09 in php_header (tsrm_ls=0x7d4118) at /usr/src/debug/php5.3-200905091830/ext/standard/head.c:69
0000005 0x00007ffff33adf41 in php_ub_body_write (str=0xac88e8 "string(1) \"b\"\nfloat(0.00025796890258789)\n", str_length=41, tsrm_ls=0x7d1c20) at /usr/src/debug/php5.3-200905091830/main/output.c:721
0000006 0x00007ffff33ae631 in php_end_ob_buffer (send_buffer=1 '\1', just_flush=0 '\0', tsrm_ls=0x7d1c20) at /usr/src/debug/php5.3-200905091830/main/output.c:300
0000007 0x00007ffff33aef7d in php_end_ob_buffers (send_buffer=<value optimized out>, tsrm_ls=0x7d1c20) at /usr/src/debug/php5.3-200905091830/main/output.c:339
0000008 0x00007ffff3399057 in php_request_shutdown (dummy=<value optimized out>) at /usr/src/debug/php5.3-200905091830/main/main.c:1540
0000009 0x00007ffff379b0b7 in php_apache_request_dtor (tsrm_ls=<value optimized out>, r=<value optimized out>) at /usr/src/debug/php5.3-200905091830/sapi/apache2handler/sapi_apache2.c:488
0000010 php_handler (tsrm_ls=<value optimized out>, r=<value optimized out>) at /usr/src/debug/php5.3-200905091830/sapi/apache2handler/sapi_apache2.c:660
0000011 0x0000000000437415 in ap_run_handler (r=0xafd898) at /usr/src/debug/httpd-2.2.11/server/config.c:158
0000012 0x000000000043a99f in ap_invoke_handler (r=0xafd898) at /usr/src/debug/httpd-2.2.11/server/config.c:372
0000013 0x0000000000445a0e in ap_process_request (r=0xafd898) at /usr/src/debug/httpd-2.2.11/modules/http/http_request.c:282
0000014 0x0000000000442a08 in ap_process_http_connection (c=0xaf7578) at /usr/src/debug/httpd-2.2.11/modules/http/http_core.c:190
0000015 0x000000000043e7fd in ap_run_process_connection (c=0xaf7578) at /usr/src/debug/httpd-2.2.11/server/connection.c:43
0000016 0x000000000044a030 in child_main (child_num_arg=<value optimized out>) at /usr/src/debug/httpd-2.2.11/server/mpm/prefork/prefork.c:662
0000017 0x000000000044a2b8 in make_child (s=0x6709f0, slot=0) at /usr/src/debug/httpd-2.2.11/server/mpm/prefork/prefork.c:702
0000018 0x000000000044a8cf in ap_mpm_run (_pconf=<value optimized out>, plog=<value optimized out>, s=<value optimized out>) at /usr/src/debug/httpd-2.2.11/server/mpm/prefork/prefork.c:978
0000019 0x00000000004240f5 in main (argc=2, argv=0x7fffffffe698) at /usr/src/debug/httpd-2.2.11/server/main.c:740