Interview Questions Php/mysql

difference between $ and $$ php or static and dynamic variable

2011-05-30T15:51:00.001+05:30

<?php
//difference between $ and $$ php or static and dynamic variable
$message = 'name';
$name = 'afroz';
echo '$message='.$message;//outputs - $message=name
echo '$$message='.$$message;//outputs - '$$message=afroz
?>

Difference between '=', "==" and '===' in PHP

2011-05-24T16:54:00.001+05:30

=        sign is an assignment - take what's on the right as an expression and save it in the variable named on the left.

==        sign is a comparison and tests whether the variable / expression / constant to the left has the same value as the variable / expression / constant to the right.

===        sign is a comparison to see whether two variables / expresions / constants are equal AND have the same type - i.e. both are strings or both are integers.

Difference between myisam and innodb mysql engines

2011-04-01T11:53:00.000+05:30

1) InnoDB storage engine of MySQL has support for transactions and automatic crash recovery while MyIsam don't.

2)Innodb has transaction support, commits and rollbacks, myisam don't.
3)MyIsam has full-text indexing, InnoDB doesn't.

4)InnoDB supports foreign key constraints.