Description:
------------
<?php
var_dump(strtr("foo", []));

Valgrind:

==24828== Invalid read of size 1
==24828==    at 0x817D0EA: php_strtr_hash (string.c:2836)
==24828==    by 0x817DC37: php_strtr_array_do_repl (string.c:3049)
==24828==    by 0x817E255: php_strtr_array (string.c:3113)
==24828==    by 0x817E412: zif_strtr (string.c:3144)
==24828==    by 0x82A7E96: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:558)
==24828==    by 0x82AD85B: ZEND_DO_FCALL_SPEC_CONST_HANDLER (zend_vm_execute.h:2585)
==24828==    by 0x82A7392: execute_ex (zend_vm_execute.h:363)
==24828==    by 0x82A7447: zend_execute (zend_vm_execute.h:388)
==24828==    by 0x8266A15: zend_execute_scripts (zend.c:1330)
==24828==    by 0x81C77A3: php_execute_script (main.c:2549)
==24828==    by 0x831669C: do_cli (php_cli.c:994)
==24828==    by 0x8317BF6: main (php_cli.c:1378)
==24828==  Address 0x43fb16d is 3 bytes before a block of size 4 alloc'd
==24828==    at 0x402BE68: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==24828==    by 0x822C278: _emalloc (zend_alloc.c:2427)
==24828==    by 0x822C795: _estrndup (zend_alloc.c:2650)
==24828==    by 0x82624DD: _zval_copy_ctor_func (zend_variables.c:126)
==24828==    by 0x82A1BF1: _zval_copy_ctor (zend_variables.h:45)
==24828==    by 0x82ADC3E: ZEND_SEND_VAL_SPEC_CONST_HANDLER (zend_vm_execute.h:2754)
==24828==    by 0x82A7392: execute_ex (zend_vm_execute.h:363)
==24828==    by 0x82A7447: zend_execute (zend_vm_execute.h:388)
==24828==    by 0x8266A15: zend_execute_scripts (zend.c:1330)
==24828==    by 0x81C77A3: php_execute_script (main.c:2549)
==24828==    by 0x831669C: do_cli (php_cli.c:994)
==24828==    by 0x8317BF6: main (php_cli.c:1378)
==24828== 
string(3) "foo"
==24828== 
==24828== HEAP SUMMARY:
==24828==     in use at exit: 0 bytes in 0 blocks
==24828==   total heap usage: 12,026 allocs, 12,026 frees, 1,114,247 bytes allocated
==24828== 
==24828== All heap blocks were freed -- no leaks are possible
==24828== 
==24828== For counts of detected and suppressed errors, rerun with: -v
==24828== ERROR SUMMARY: 2 errors from 1 contexts (suppressed: 0 from 0)