php decrypting base64Encoding text from iOS - php

Question

I have spent a huge amount of time with no success trying to decrypt an encrypted string ("yIH7EYW0e4HuxkHApkG7xQ==") on the PHP server side. The string was encrypted on iOS platform and encoded into text using base64 format.
Anyway, could someone please correct my mistake with the PHP side (I am a little weak on this side)? I am aware the method is not very secure as is. I just need a temporary solution until I can research better methods with openssl.
PHP:
$str_encrypted = "yIH7EYW0e4HuxkHApkG7xQ=="; // base64encoded
$mykey = "my password";
$decrypted = decrypt_data($str_encrypted =, $mykey);
function decrypt_data($str_encrypted =, $mykey)
{
$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$decrypted_text = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $encryptionkey, $text, MCRYPT_MODE_ECB, $iv);
return $decrypted_text;
}
IOS:
- (NSString *)AES128EncryptWithKey:(NSString *)key
{
NSData *plainData = [self dataUsingEncoding:NSUTF8StringEncoding];
NSData *encryptedData = [plainData AES128EncryptWithKey:key];
NSString *encryptedString = [encryptedData base64Encoding];
return encryptedString;
}
IOS:
- (NSString *)base64Encoding
{
const unsigned char *bytes = [self bytes];
NSMutableString *result = [NSMutableString stringWithCapacity:self.length];
unsigned long ixtext = 0;
unsigned long lentext = self.length;
long ctremaining = 0;
unsigned char inbuf[3], outbuf[4];
unsigned short i = 0;
unsigned short charsonline = 0, ctcopy = 0;
unsigned long ix = 0;
while( YES )
{
ctremaining = lentext - ixtext;
if( ctremaining <= 0 ) break;
for( i = 0; i < 3; i++ )
{
ix = ixtext + i;
if( ix < lentext ) inbuf[i] = bytes[ix];
else inbuf [i] = 0;
}
outbuf [0] = (inbuf [0] & 0xFC) >> 2;
outbuf [1] = ((inbuf [0] & 0x03) << 4) | ((inbuf [1] & 0xF0) >> 4);
outbuf [2] = ((inbuf [1] & 0x0F) << 2) | ((inbuf [2] & 0xC0) >> 6);
outbuf [3] = inbuf [2] & 0x3F;
ctcopy = 4;
switch( ctremaining )
{
case 1:
ctcopy = 2;
break;
case 2:
ctcopy = 3;
break;
}
for( i = 0; i < ctcopy; i++ )
[result appendFormat:#"%c", encodingTable[outbuf[i]]];
for( i = ctcopy; i < 4; i++ )
[result appendString:#"="];
ixtext += 3;
charsonline += 4;
}
return [NSString stringWithString:result];
}