This example worked for me:
RedHat 7.2 / php 4.2.2 / Apache 1.3.7
// STEP 1: Encryption with Public Key (you will need Private Key to decrypt - see step2).
$string="Some Important Data";
$fp=fopen ("cert.pem","r");
$pub_key=fread ($fp,8192);
fclose($fp);
$PK="";
$PK=openssl_get_publickey($pub_key);
if (!$PK) {
echo "Cannot get public key";
}
$finaltext="";
openssl_public_encrypt($string,$finaltext,$PK);
if (!empty($finaltext)) {
openssl_free_key($PK);
echo "Encryption OK!";
}else{
echo "Cannot Encrypt";
}
// STEP 2: Decription (Using Private Key)
$fp=fopen ("pk.pem","r");
$priv_key2=fread ($fp,8192);
fclose($fp);
$PK2=openssl_get_privatekey($priv_key2);
$Crypted=openssl_private_decrypt($Data,$Decrypted,$PK2);
if (!$Crypted) {
$MSG.="<p class='error'>Cannot Decrypt ($CCID).</p>";
}else{
echo "Decrypted Data: " . $Decrypted;
}
