﻿ 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

Mutates the original array to filter out the values specified

Example:

```<?php
function tips_pull(&\$items, ...\$params)
{
\$items = array_values(array_diff(\$items, \$params));
return \$items;
}

\$items = ['x', 'y', 'z', 'x', 'y', 'z'];
print_r(tips_pull(\$items, 'y', 'z'));
?>
```

Output:

```Array
(
 => x
 => x
)
```