# How to Converts an octal number to a decimal number in PHP ?

There are multiple methods to convert an octal number to a decimal number in PHP:

Method 1: Using octdec() function The octdec() function is a built-in PHP function that converts an octal number to a decimal number. It takes an octal number as a string parameter and returns its decimal equivalent.

Example:

``````\$octal_num = "17"; // Octal number
\$decimal_num = octdec(\$octal_num); // Convert octal to decimal
echo \$decimal_num; // Output: 15
``````

Method 2: Using base_convert() function The base_convert() function is another built-in PHP function that can be used to convert an octal number to a decimal number. It takes two parameters - the number to be converted and the base of the number (in this case, 8 for octal).

Example:

``````\$octal_num = "17"; // Octal number
\$decimal_num = base_convert(\$octal_num, 8, 10); // Convert octal to decimal
echo \$decimal_num; // Output: 15
``````

Method 3: Using manual conversion We can also manually convert an octal number to a decimal number by multiplying each digit of the octal number with its corresponding power of 8 and adding the results.

Example:

``````\$octal_num = "17"; // Octal number
\$decimal_num = 0;
\$len = strlen(\$octal_num);
for (\$i = 0; \$i < \$len; \$i++) {
\$decimal_num += intval(\$octal_num[\$i]) * pow(8, \$len - \$i - 1);
}
echo \$decimal_num; // Output: 15
``````