﻿ PHP Exercise: Print the number of prime numbers which are less than or equal to a given integer - w3resource # PHP Exercises: Print the number of prime numbers which are less than or equal to a given integer

## PHP: Exercise-52 with Solution

Write a PHP program to print the number of prime numbers which are less than or equal to a given integer.

Input:
n (1 ≤ n ≤ 999,999) .

Pictorial Presentation: Sample Solution: -

PHP Code:

``````<?php

\$a = array_fill(0, 1000000, true);
\$a = \$a = false;

for(\$i = 2; \$i * \$i < 1000000; \$i++){
if(!\$a[\$i]) continue;
for(\$j = \$i * \$i; \$j < 1000000; \$j += \$i){
\$a[\$j] = false;
}
}

\$sum = array_fill(0, 1000000, 0);

for(\$i = 1; \$i < 1000000; \$i++){
\$sum[\$i] += \$sum[\$i - 1];
if(\$a[\$i]) \$sum[\$i]++;
}

while(fscanf(STDIN, "%d", \$n)){
echo "Number of prime numbers which are less than or equal to n: ";
echo \$sum[\$n] . "\n";
}
?>
```
```

Sample Output:

```Sample Input: 50
Number of prime numbers which are less than or equal to n: 15
```

Flowchart: PHP Code Editor:

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## PHP: Tips of the Day

Why shouldn't I use mysql_* functions in PHP?

The MySQL extension:

• Is not under active development
• Is officially deprecated as of PHP 5.5 (released June 2013).
• Has been removed entirely as of PHP 7.0 (released December 2015)
• This means that as of 31 Dec 2018 it does not exist in any supported version of PHP. If you are using a version of PHP which supports it, you are using a version which doesn't get security problems fixed.
• Lacks an OO interface
• Doesn't support:
• Non-blocking, asynchronous queries
• Prepared statements or parameterized queries
• Stored procedures
• Multiple Statements
• Transactions
• The "new" password authentication method (on by default in MySQL 5.6; required in 5.7)
• Any of the new functionality in MySQL 5.1 or later

Since it is deprecated, using it makes your code less future proof.

Lack of support for prepared statements is particularly important as they provide a clearer, less error-prone method of escaping and quoting external data than manually escaping it with a separate function call.

Ref : https://bit.ly/2BIIsF0