diff --git a/NEWS b/NEWS
index a1be27f842d..82c9faa85c9 100644
--- a/NEWS
+++ b/NEWS
@@ -57,6 +57,7 @@ PHP                                                                        NEWS
     set params during context creation. (Sara)
   . "context" and "binary_pipes" params in "other_options" arg. (Sara)
   . stream_resolve_include_path(). (Sara)
+- Added gmp_testbit() function. (Tony)
 - Added shm_has_var() function. (Mike)
 - Added str_getcsv() function. (Sara)
 - Added ext/hash support to ext/session's ID generator. (Sara)
diff --git a/ext/gmp/gmp.c b/ext/gmp/gmp.c
index dca90ac1a47..ef1f44214bc 100644
--- a/ext/gmp/gmp.c
+++ b/ext/gmp/gmp.c
@@ -242,6 +242,12 @@ ZEND_BEGIN_ARG_INFO(arginfo_gmp_clrbit, 0)
 	ZEND_ARG_INFO(0, index)
 ZEND_END_ARG_INFO()
 
+	static
+ZEND_BEGIN_ARG_INFO(arginfo_gmp_testbit, 0)
+	ZEND_ARG_INFO(0, a)
+	ZEND_ARG_INFO(0, index)
+ZEND_END_ARG_INFO()
+
 static
 ZEND_BEGIN_ARG_INFO(arginfo_gmp_popcount, 0)
 	ZEND_ARG_INFO(0, a)
@@ -308,6 +314,7 @@ zend_function_entry gmp_functions[] = {
 	ZEND_FE(gmp_xor,	arginfo_gmp_xor)
 	ZEND_FE(gmp_setbit,	arginfo_gmp_setbit)
 	ZEND_FE(gmp_clrbit,	arginfo_gmp_clrbit)
+	ZEND_FE(gmp_testbit,	arginfo_gmp_testbit)
 	ZEND_FE(gmp_scan0, arginfo_gmp_scan0)
 	ZEND_FE(gmp_scan1, arginfo_gmp_scan1)
 	ZEND_FE(gmp_popcount, arginfo_gmp_popcount)
@@ -1531,6 +1538,35 @@ ZEND_FUNCTION(gmp_clrbit)
 }
 /* }}} */
 
+/* {{{ proto bool gmp_testbit(resource a, int index) U
+   Tests if bit is set in a */
+ZEND_FUNCTION(gmp_testbit)
+{
+	zval **a_arg, **ind_arg;
+	int index;
+	mpz_t *gmpnum_a;
+
+	if (ZEND_NUM_ARGS() != 2 || zend_get_parameters_ex(2, &a_arg, &ind_arg) == FAILURE){
+		WRONG_PARAM_COUNT;
+	}
+
+	ZEND_FETCH_RESOURCE(gmpnum_a, mpz_t *, a_arg, -1, GMP_RESOURCE_NAME, le_gmp);
+
+	convert_to_long_ex(ind_arg);
+	index = Z_LVAL_PP(ind_arg);
+	
+	if (index < 0) {
+		php_error_docref(NULL TSRMLS_CC, E_WARNING, "Index must be greater than or equal to zero");
+		RETURN_FALSE;
+	}
+
+	if (mpz_tstbit(*gmpnum_a, index)) {
+		RETURN_TRUE;
+	}
+	RETURN_FALSE;
+}
+/* }}} */
+
 /* {{{ proto int gmp_popcount(resource a) U
    Calculates the population count of a */
 ZEND_FUNCTION(gmp_popcount)
diff --git a/ext/gmp/php_gmp.h b/ext/gmp/php_gmp.h
index 22b4abcf487..ce208c3d4df 100644
--- a/ext/gmp/php_gmp.h
+++ b/ext/gmp/php_gmp.h
@@ -70,6 +70,7 @@ ZEND_FUNCTION(gmp_xor);
 ZEND_FUNCTION(gmp_random);
 ZEND_FUNCTION(gmp_setbit);
 ZEND_FUNCTION(gmp_clrbit);
+ZEND_FUNCTION(gmp_testbit);
 ZEND_FUNCTION(gmp_scan0);
 ZEND_FUNCTION(gmp_scan1);
 ZEND_FUNCTION(gmp_popcount);
diff --git a/ext/gmp/tests/039.phpt b/ext/gmp/tests/039.phpt
new file mode 100644
index 00000000000..084772288c0
--- /dev/null
+++ b/ext/gmp/tests/039.phpt
@@ -0,0 +1,79 @@
+--TEST--
+gmp_testbit() basic tests
+--FILE--
+<?php
+
+$n = gmp_init(0);
+var_dump(gmp_testbit($n, -10));
+var_dump(gmp_testbit($n, 0));
+var_dump(gmp_testbit($n, 1));
+var_dump(gmp_testbit($n, 100));
+
+$n = gmp_init(-1);
+var_dump(gmp_testbit($n, 1));
+var_dump(gmp_testbit($n, -1));
+
+$n = gmp_init("1000000");
+var_dump(gmp_testbit($n, 1));
+gmp_setbit($n, 1);
+var_dump(gmp_testbit($n, 1));
+var_dump(gmp_strval($n));
+
+gmp_setbit($n, 5);
+var_dump(gmp_testbit($n, 5));
+var_dump(gmp_strval($n));
+
+$n = gmp_init("238462734628347239571823641234");
+var_dump(gmp_testbit($n, 5));
+gmp_setbit($n, 5);
+var_dump(gmp_testbit($n, 5));
+var_dump(gmp_strval($n));
+
+gmp_clrbit($n, 5);
+var_dump(gmp_testbit($n, 5));
+var_dump(gmp_strval($n));
+
+echo "Done\n";
+?>
+--EXPECTF--	
+Warning: gmp_testbit(): Index must be greater than or equal to zero in %s on line %d
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(true)
+
+Warning: gmp_testbit(): Index must be greater than or equal to zero in %s on line %d
+bool(false)
+bool(false)
+bool(true)
+string(7) "1000002"
+bool(true)
+string(7) "1000034"
+bool(false)
+bool(true)
+string(30) "238462734628347239571823641266"
+bool(false)
+string(30) "238462734628347239571823641234"
+Done
+--UEXPECTF--
+Warning: gmp_testbit(): Index must be greater than or equal to zero in %s on line %d
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(true)
+
+Warning: gmp_testbit(): Index must be greater than or equal to zero in %s on line %d
+bool(false)
+bool(false)
+bool(true)
+unicode(7) "1000002"
+bool(true)
+unicode(7) "1000034"
+bool(false)
+bool(true)
+unicode(30) "238462734628347239571823641266"
+bool(false)
+unicode(30) "238462734628347239571823641234"
+Done