#1. Make sure you can connect to the MySQL
It might seem kind of obvious. But, when you have a new project and development environment setup. You may not be able to connect to the database right away
1) Because you forget to start the MySQL database server
2) Because you did not configure the connection passwords correctly
3) You are trying to use root to connect to the database from the web server. (Passwords in mysql are setup per IP. Usually they are only set for access via localhost only, especially for the root user.)
#2. Use a gist of code to test the database connection first
If the gist works, then you should debug the application logic instead of the database connection
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') ' . mysqli_connect_error());
}
echo 'Connected... ' . mysqli_get_host_info($link) . "\n";
#3. Check if all the parameters for your SQL query string are actually correct
When the SQL query string looks correct, 99% it is because it is correct and you
are actually using the wrong parameter values and hence causing errors to occur
when you execute the code.
$sqlstr = 'SELECT * FROM mydbtable WHERE myname = $input_var';
echo $sqlstr;
if (!$mysqli->query($sqlstr)) {
echo 'Error: ', $mysqli->error;
}
In the code above, you may find that $input_var is actually an empty string and
thus the SQL statement you are running
is SELECT * FROM mydbtable WHERE myname =
This would result in an error.
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Connected... ' . mysqli_get_host_info($link) . "\n"; - See more at: http://jason.pureconcepts.net/2013/04/common-debugging-php-mysql/#sthash.6ZkmQHcs.dpuf
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Connected... ' . mysqli_get_host_info($link) . "\n"; - See more at: http://jason.pureconcepts.net/2013/04/common-debugging-php-mysql/#sthash.6ZkmQHcs.dpuf
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Connected... ' . mysqli_get_host_info($link) . "\n"; - See more at: http://jason.pureconcepts.net/2013/04/common-debugging-php-mysql/#sthash.6ZkmQHcs.dpuf
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Connected... ' . mysqli_get_host_info($link) . "\n"; - See more at: http://jason.pureconcepts.net/2013/04/common-debugging-php-mysql/#sthash.6ZkmQHcs.dpuf
