执行“ php -r” mysql_connect（）不返回链接资源

Question

I've been embedding some php in my shell scripts. Stuff like this works:

SUBJECT_URL= php -r "echo rawurlencode('$SUBJECT');"

and sets my string variable SUBJECT_URL to the converted value of $SUBJECT

However,

I am trying to use this command:

link= php -r "mysql_connect('localhost', 'root', 'mypassword');"

To test my connection to the SQL database. Unfortunately, the value for "link" is not getting set. Therefore I can't test it for success and can't issue the:

php -r "mysql_close($link);"

to release the resource.

Any help would be appreciated.

Answer 1

This is because mysql connection dies with php. Now if you really cannot just connect to mysql without using php from where you type, you could use something like :

php -r "echo @mysql_connect('localhost', 'root', 'mypassword')? 'connected' : 'not connected';"

You don't need to release the connection as php will do it for you when it exits.

Answer 2

Using php -r is almost certainly the wrong approach; if you need to use PHP you'd be better off writing the whole script in PHP instead of a mix of Shell as well.

The reasons link=php -r "mysql_connect('localhost', 'root', 'mypassword');" doesn't work is that (a) mysql_connect returns a resource to the database connection, which is not something that can be coerced into a string, and (b) your one-line PHP script ( mysql_connect('localhost', 'root', 'mypassword'); doesn't echo that resource anyway, ie it doesn't even attempt to coerce the resource into a string.

The mysql_connect function returns false on failure, so if you want your link variable to indicate success or failure you can assign a string to it accordingly. In a one-liner the ternary operator is a simple way to do that, as fab2s noted in his answer ( echo @mysql_connect('localhost', 'root', 'mypassword')? 'connected' : 'not connected' ). In that code the @ (silence operator) prevents a failed connection from raising a Warning from PHP, and the use of the ternary operator conditionally returns "connected" if the call returned something "truthy" and "not connected" if it returned false .

As an aside, note that you really shouldn't use the old MySQL extension any longer. In fact, it's generally best to use PDO:

<?php
$dbConn = new \PDO(
    'mysql:dbname=my_db;host=localhost;charset=utf8',
    'user',
    'password',
    [PDO::ATTR_ERRMODE => PDO::ERR_EXCEPTION]
);