mysql too many connection error. - php

Question

I have a .txt file with a list of 60,000 English words. I wanted to insert those to my database, so I simply just did as show here.
$file = new SplFileObject('list.txt');
foreach ($file as $line => $word) {
$p = new PDO('mysql:host=localhost; dbname=test_dictionary', 'root', 'test');
$p->query("INSERT INTO words (english) VALUES('$word') ");
}
Now, after I run this script, I get the following error:
Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [1040] Too many connections' in /var/www/skillz/test/curl/index.php:17 Stack trace: #0 /var/www/test/index.php(17): PDO->__construct('mysql:host=loca...', 'root', 'test') #1 {main} thrown in /var/www/test/index.php on line 4
That line 4 is where the new PDO('mysql:') is located. So, I tried to search this error, and found this answer that seemed a solution. And I edited mysql accordingly, as
$ vi /etc/my.cnf
max_connections=250
But I still get the same error, I have MySql 5.5.38 running PHP-FPM, NGINX in CentOS 6.5

Answer 1

Don't open a new Connection for every word. You only need one connection open for the lifetime of your inserts. I'm not sure about the true lifetime of a PDO object, I know they're cleaned up when they're not used, but garbage collection might not do that for a couple of minutes, and for 60,000 words, you're going to hit your limit of connections to the database faster than it can clean them up.
$file = new SplFileObject('list.txt');
$p = new PDO('mysql:host=localhost; dbname=test_dictionary', 'root', 'test');
foreach ($file as $line => $word) {
$p->query("INSERT INTO words (english) VALUES('$word') ");
}

Answer 2

You should declare the SQL connection outside the foreach.
Because it will make 60.000 connections.
$file = new SplFileObject('list.txt');
$p = new PDO('mysql:host=localhost; dbname=test_dictionary', 'root', 'test');
foreach ($file as $line => $word) {
$p->query("INSERT INTO words (english) VALUES('$word') ");
}
You only need to declare the SQL connection once and you can use it anytime as you want.
If you put it in foreach it will make a SQL connection every word, that's why you got that message.

Answer 3

Solution 1
Use batch insert statement :
INSERT INTO words (col1, col2) VALUES ('val1', 'val2'), ('val3', 'val4'), ...('val3n', 'val4n');
This fails if you also want to check if some rows failed or not. So, below is another solution.
Solution 2
Create a persistent database connection. This will use the same connection in all iterations of the loop.
$file = new SplFileObject('list.txt');
$p = new PDO('mysql:host=localhost; dbname=test_dictionary', 'root', 'test', array(
PDO::ATTR_PERSISTENT => true)); //Persistent Database Connection
foreach ($file as $line => $word) {
$p->query("INSERT INTO words (english) VALUES('$word') ");
}
$p = null; //Destroy Connection