Works fine for me:
<?php
include('Crypt/RSA.php');
$rsa = new Crypt_RSA();
$rsa->loadKey('<RSAKeyValue><Modulus>qfOIjoSxsmBqS3YGsxd4+FBEmFmX4Z/cTAV4l3BOqmMVDxTxHt4QuvK8l2Iv6GeTSp5xuwpqUkgwyo4zb2UQt1sLn2vvAmGqz7Oih6gHYrpA9GmR6QHomsQNJrDTvZXtCPNUmWZ5DzFjnKNL/FfZQGYp0qjIkpIhuLAUhKYzMaM=</Modulus><Exponent>AQAB</Exponent><P>57hBPSAr6VGVYTYL6pUft0y9hbU7cUYEiYhF2pVJ0pv6pGWIb27nK+9U/AaWH0+wtefpRlVyjbeNiDK3rmYmtQ==</P><Q>u8Jgam1//jhcYYCZX5168L0roe6L+IJ0A98zlbQb7crpqbTxqDAsX9LQpGiQP1JZINowAbPECDRZIGfT+fsV9w==</Q><DP>AZASkJD4+tfcBA3TQr/CuP/Bf3dbcUYhnbPXlMPQ/aSjqhwtMWM0F+3DSvfYZ1moPXHU9u54mVAVmkeNSZXSyQ==</DP><DQ>J1DFVaPGKFpu5a/C7eWQ57YE2+ySfJ/8YQ8sww0qx/k0Qmf0Li6gLBR9wd9vTQMWTK3DXafhxYIIo6N6HJ858w==</DQ><InverseQ>Q2MlSoE2ADtFXvjPi5UgxApqp4QewmZONu3vGmAL07JMyDHdgVweevZTJTun3EBRKV0PWCMvtk4BJW0lUSuBNQ==</InverseQ><D>TCzzVWYWu+xJWJ+DazynJS3dQShPUnsz5ANDxSU6rVaR9tudJAfHGfR5IaWJ8bKTK4wPUBXgCBeBfxjz5wc20SyBWa1vL7K4DqLRJ/qEyFSZxXr8wKQOKyexZRGbsLjtUnmYrrXKMOhRkiV/VI1K+TKX/FhoDVPjz8s4GamzNQk=</D></RSAKeyValue>');
$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_PKCS1);
echo $rsa->decrypt(base64_decode('d1YJ4ePp80Oe0OBTl+fBAKzDUogC56k7XB8ANggDotm44frzkNYUICUog/BV9x7mQyNT0lHj7vXo0uXrOIAS0BxgCNbqrpw0UBIyCX5rMDZF1v/1eQMTDa3jEwss1DQHHikQWVLFH5IGCspzJUTitwQTAyRCLdYTRijTCQhf0oI='));
phpseclib has had built-in support for XML keys for a while now so you don't need to jump through all the hoops you did in your code.
The plaintext is h e l l o
. Make sure you're running the latest version of phpseclib if you're not already. I don't know of issues with older versions that'd cause problems but running the latest is never a bad idea anyway.