diff --git a/ext/standard/basic_functions.c b/ext/standard/basic_functions.c
index a40fdd23979f1..98a373903e336 100644
--- a/ext/standard/basic_functions.c
+++ b/ext/standard/basic_functions.c
@@ -1729,6 +1729,10 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_log, 0, 0, 1)
 	ZEND_ARG_INFO(0, base)
 ZEND_END_ARG_INFO()
 
+ZEND_BEGIN_ARG_INFO(arginfo_log2, 0)
+	ZEND_ARG_INFO(0, number)
+ZEND_END_ARG_INFO()
+
 ZEND_BEGIN_ARG_INFO(arginfo_log10, 0)
 	ZEND_ARG_INFO(0, number)
 ZEND_END_ARG_INFO()
@@ -2916,6 +2920,7 @@ const zend_function_entry basic_functions[] = { /* {{{ */
 	PHP_FE(pow,																arginfo_pow)
 	PHP_FE(exp,																arginfo_exp)
 	PHP_FE(log,																arginfo_log)
+	PHP_FE(log2,															arginfo_log2)
 	PHP_FE(log10,															arginfo_log10)
 	PHP_FE(sqrt,															arginfo_sqrt)
 	PHP_FE(hypot,															arginfo_hypot)
diff --git a/ext/standard/math.c b/ext/standard/math.c
index be2d655263f13..1077e58d871e4 100644
--- a/ext/standard/math.c
+++ b/ext/standard/math.c
@@ -716,6 +716,19 @@ PHP_FUNCTION(log)
 }
 /* }}} */
 
+/* {{{ proto float log2(float number)
+   Returns the base-2 logarithm of the number */
+PHP_FUNCTION(log2)
+{
+	double num;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "d", &num) == FAILURE) {
+		return;
+	}
+	RETURN_DOUBLE(log2(num));
+}
+/* }}} */
+
 /* {{{ proto float log10(float number)
    Returns the base-10 logarithm of the number */
 PHP_FUNCTION(log10)
diff --git a/ext/standard/php_math.h b/ext/standard/php_math.h
index 116acd9df5e8b..bcc49693f751d 100644
--- a/ext/standard/php_math.h
+++ b/ext/standard/php_math.h
@@ -39,6 +39,7 @@ PHP_FUNCTION(atan2);
 PHP_FUNCTION(pi);
 PHP_FUNCTION(exp);
 PHP_FUNCTION(log);
+PHP_FUNCTION(log2);
 PHP_FUNCTION(log10);
 PHP_FUNCTION(is_finite);
 PHP_FUNCTION(is_infinite);
diff --git a/ext/standard/tests/math/log2_basic.phpt b/ext/standard/tests/math/log2_basic.phpt
new file mode 100644
index 0000000000000..f2acf272beb2a
--- /dev/null
+++ b/ext/standard/tests/math/log2_basic.phpt
@@ -0,0 +1,52 @@
+--TEST--
+Test return type and value for expected input log2()
+--INI--
+precision = 14
+--FILE--
+<?php
+/* 
+ * proto float log2(float number)
+ * Function is implemented in ext/standard/math.c
+*/ 
+
+$file_path = dirname(__FILE__);
+require($file_path."/allowed_rounding_error.inc");
+
+$arg_0 = 1.0;
+$arg_1 = 10.0;
+$arg_2 = 100.0;
+
+echo "log2 $arg_0 = ";
+$r0 = log2($arg_0);
+var_dump($r0);
+if (allowed_rounding_error($r0 ,0.0 )) {
+	echo "Pass\n";
+} else {
+	echo "Fail\n";
+}
+
+echo "log2 $arg_1 = ";
+$r1 = log2($arg_1);
+var_dump($r1);
+if (allowed_rounding_error($r1, 3.3219280948874)) {
+	echo "Pass\n";
+} else {
+	echo "Fail\n";
+}
+
+echo "log2 $arg_2 = ";
+$r2 = log2($arg_2);
+var_dump($r2);
+if (allowed_rounding_error($r2, 6.6438561897747)) {
+	echo "Pass\n";
+} else {
+	echo "Fail\n";
+}
+?>
+--EXPECTF--
+log2 1 = float(%f)
+Pass
+log2 10 = float(%f)
+Pass
+log2 100 = float(%f)
+Pass
diff --git a/ext/standard/tests/math/log2_basiclong_64bit.phpt b/ext/standard/tests/math/log2_basiclong_64bit.phpt
new file mode 100644
index 0000000000000..11f82f8add031
--- /dev/null
+++ b/ext/standard/tests/math/log2_basiclong_64bit.phpt
@@ -0,0 +1,60 @@
+--TEST--
+Test log2 function : 64bit long tests
+--SKIPIF--
+<?php
+if (PHP_INT_SIZE != 8) die("skip this test is for 64bit platform only");
+?>
+--FILE--
+<?php
+ 
+define("MAX_64Bit", 9223372036854775807);
+define("MAX_32Bit", 2147483647);
+define("MIN_64Bit", -9223372036854775807 - 1);
+define("MIN_32Bit", -2147483647 - 1);
+
+$longVals = array(
+    MAX_64Bit, MIN_64Bit, MAX_32Bit, MIN_32Bit, MAX_64Bit - MAX_32Bit, MIN_64Bit - MIN_32Bit,
+    MAX_32Bit + 1, MIN_32Bit - 1, MAX_32Bit * 2, (MAX_32Bit * 2) + 1, (MAX_32Bit * 2) - 1,
+    MAX_64Bit -1, MAX_64Bit + 1, MIN_64Bit + 1, MIN_64Bit - 1
+);
+
+
+foreach ($longVals as $longVal) {
+   echo "--- testing: $longVal ---\n";
+   var_dump(log2($longVal));
+}
+   
+?>
+===DONE===
+--EXPECT--
+--- testing: 9223372036854775807 ---
+float(63)
+--- testing: -9223372036854775808 ---
+float(NAN)
+--- testing: 2147483647 ---
+float(30.999999999328)
+--- testing: -2147483648 ---
+float(NAN)
+--- testing: 9223372034707292160 ---
+float(62.999999999664)
+--- testing: -9223372034707292160 ---
+float(NAN)
+--- testing: 2147483648 ---
+float(31)
+--- testing: -2147483649 ---
+float(NAN)
+--- testing: 4294967294 ---
+float(31.999999999328)
+--- testing: 4294967295 ---
+float(31.999999999664)
+--- testing: 4294967293 ---
+float(31.999999998992)
+--- testing: 9223372036854775806 ---
+float(63)
+--- testing: 9.2233720368548E+18 ---
+float(63)
+--- testing: -9223372036854775807 ---
+float(NAN)
+--- testing: -9.2233720368548E+18 ---
+float(NAN)
+===DONE===
diff --git a/ext/standard/tests/math/log2_error.phpt b/ext/standard/tests/math/log2_error.phpt
new file mode 100644
index 0000000000000..6ca8f96f37d11
--- /dev/null
+++ b/ext/standard/tests/math/log2_error.phpt
@@ -0,0 +1,31 @@
+--TEST--
+Test wrong number of arguments for log2()
+--INI--
+precision = 14
+--FILE--
+<?php
+/* 
+ * proto float log2(float number)
+ * Function is implemented in ext/standard/math.c
+*/ 
+
+$arg_0 = 1.0;
+$extra_arg = 1;
+
+echo "\nToo many arguments\n";
+var_dump(log2($arg_0, $extra_arg));
+
+echo "\nToo few arguments\n";
+var_dump(log2());
+
+?>
+--EXPECTF--
+Too many arguments
+
+Warning: log2() expects exactly 1 parameter, 2 given in %s on line %d
+NULL
+
+Too few arguments
+
+Warning: log2() expects exactly 1 parameter, 0 given in %s on line %d
+NULL
diff --git a/ext/standard/tests/math/log2_variation.phpt b/ext/standard/tests/math/log2_variation.phpt
new file mode 100644
index 0000000000000..aebde8fa7bf4f
--- /dev/null
+++ b/ext/standard/tests/math/log2_variation.phpt
@@ -0,0 +1,56 @@
+--TEST--
+Test variations in usage of log2()
+--INI--
+precision = 10
+--FILE--
+<?php
+/* 
+ * proto float log2(float number)
+ * Function is implemented in ext/standard/math.c
+*/ 
+
+
+//Test log2 with a different input values
+
+$values = array(23,
+		-23,
+		2.345e1,
+		-2.345e1,
+		0x17,
+		027,
+		"23",
+		"23.45",
+		"2.345e1",
+		"nonsense",				
+		"1000",
+		"1000ABC",
+		null,
+		true,
+		false);	
+
+for ($i = 0; $i < count($values); $i++) {
+	$res = log2($values[$i]);
+	var_dump($res);
+}
+
+?>
+--EXPECTF--
+float(4.523561956)
+float(NAN)
+float(4.551516018)
+float(NAN)
+float(4.523561956)
+float(4.523561956)
+float(4.523561956)
+float(4.551516018)
+float(4.551516018)
+
+Warning: log2() expects parameter 1 to be double, string given in %s on line %d
+NULL
+float(9.965784285)
+
+Notice: A non well formed numeric value encountered in %s on line %d
+float(9.965784285)
+float(-INF)
+float(0)
+float(-INF)