diff --git a/ext/iconv/tests/iconv_substr_basic.phpt b/ext/iconv/tests/iconv_substr_basic.phpt
new file mode 100644
index 00000000000..2fd06bd0d0b
--- /dev/null
+++ b/ext/iconv/tests/iconv_substr_basic.phpt
@@ -0,0 +1,55 @@
+--TEST--
+Test iconv_substr() function : basic functionality 
+--SKIPIF--
+<?php
+extension_loaded('iconv') or die('skip');
+function_exists('iconv_substr') or die("skip iconv_substr() is not available in this build");
+?>
+--FILE--
+<?php
+/* Prototype  : string iconv_substr(string str, int offset, [int length, string charset])
+ * Description: Returns part of a string 
+ * Source code: ext/iconv/iconv.c
+ */
+
+/*
+ * Test Basic Functionality of iconv_substr with ASCII characters and multibyte strings.
+ */
+
+echo "*** Testing iconv_substr() : basic functionality ***\n";
+
+$string_ascii = b'ABCDEF';
+//Japanese string in UTF-8
+$string_mb = base64_decode(b'5pel5pys6Kqe44OG44Kt44K544OI44Gn44GZ44CCMDEyMzTvvJXvvJbvvJfvvJjvvJnjgII=');
+
+echo "\n-- ASCII string 1 --\n";
+var_dump(bin2hex(iconv_substr($string_ascii, 3)));
+
+echo "\n-- ASCII string 2 --\n";
+var_dump(bin2hex(iconv_substr($string_ascii, 3, 5, 'ISO-8859-1')));
+
+echo "\n-- Multibyte string 1 --\n";
+$result_1 = iconv_substr($string_mb, 2, 7);
+var_dump(bin2hex($result_1));
+
+echo "\n-- Multibyte string 2 --\n";
+$result_2 = iconv_substr($string_mb, 2, 7, 'utf-8');
+var_dump(bin2hex($result_2));
+
+?>
+===DONE===
+--EXPECT--
+*** Testing iconv_substr() : basic functionality ***
+
+-- ASCII string 1 --
+unicode(6) "444546"
+
+-- ASCII string 2 --
+unicode(6) "444546"
+
+-- Multibyte string 1 --
+unicode(14) "a5e69cace8aa9e"
+
+-- Multibyte string 2 --
+unicode(42) "e8aa9ee38386e382ade382b9e38388e381a7e38199"
+===DONE===
\ No newline at end of file
diff --git a/ext/iconv/tests/iconv_substr_error1.phpt b/ext/iconv/tests/iconv_substr_error1.phpt
new file mode 100644
index 00000000000..c786b11ef2e
--- /dev/null
+++ b/ext/iconv/tests/iconv_substr_error1.phpt
@@ -0,0 +1,49 @@
+--TEST--
+Test iconv_substr() function : error conditions - Pass incorrect number of args
+--SKIPIF--
+<?php
+extension_loaded('iconv') or die('skip');
+function_exists('iconv_substr') or die("skip iconv_substr() is not available in this build");
+?>
+--FILE--
+<?php
+/* Prototype  : string iconv_substr(string str, int offset, [int length, string charset])
+ * Description: Returns part of a string 
+ * Source code: ext/iconv/iconv.c
+ */
+
+/*
+ * Pass incorrect number of arguments to iconv_substr() to test behaviour
+ */
+
+echo "*** Testing iconv_substr() : error conditions ***\n";
+
+//Test iconv_substr with one more than the expected number of arguments
+echo "\n-- Testing iconv_substr() function with more than expected no. of arguments --\n";
+$str = 'string_val';
+$start = 10;
+$length = 10;
+$encoding = 'string_val';
+$extra_arg = 10;
+var_dump( iconv_substr($str, $start, $length, $encoding, $extra_arg) );
+
+// Testing iconv_substr with one less than the expected number of arguments
+echo "\n-- Testing iconv_substr() function with less than expected no. of arguments --\n";
+$str = 'string_val';
+var_dump( iconv_substr($str) );
+
+?>
+===DONE===
+--EXPECTF--
+*** Testing iconv_substr() : error conditions ***
+
+-- Testing iconv_substr() function with more than expected no. of arguments --
+
+Warning: iconv_substr() expects at most 4 parameters, 5 given in %s on line %d
+bool(false)
+
+-- Testing iconv_substr() function with less than expected no. of arguments --
+
+Warning: iconv_substr() expects at least 2 parameters, 1 given in %s on line %d
+bool(false)
+===DONE===
diff --git a/ext/iconv/tests/iconv_substr_error2.phpt b/ext/iconv/tests/iconv_substr_error2.phpt
new file mode 100644
index 00000000000..60a11cc2fdb
--- /dev/null
+++ b/ext/iconv/tests/iconv_substr_error2.phpt
@@ -0,0 +1,38 @@
+--TEST--
+Test iconv_substr() function : error conditions - Pass an unknown encoding
+--SKIPIF--
+<?php
+extension_loaded('iconv') or die('skip');
+function_exists('iconv_substr') or die("skip iconv_substr() is not available in this build");
+?>
+--XFAIL--
+Will fail until bug #48538 fixed 
+--FILE--
+<?php
+/* Prototype  : string iconv_substr(string str, int offset, [int length, string charset])
+ * Description: Returns part of a string 
+ * Source code: ext/iconv/iconv.c
+ */
+
+/*
+ * Pass an unknown encoding to iconv_substr() to test behaviour
+ */
+
+echo "*** Testing iconv_substr() : error conditions ***\n";
+
+$str = 'Hello, world';
+$start = 1;
+$length = 5;
+$encoding = 'unknown-encoding';
+
+var_dump( iconv_substr($str, $start, $length, $encoding));
+
+echo "Done";
+?>
+--EXPECTF--
+*** Testing iconv_substr() : error conditions ***
+
+Notice: iconv_substr(): Wrong charset, conversion from `unknown-encoding' to `UCS-4LE' is not allowed in %s on line %d
+bool(false)
+Done
+