How do I convert words to numbers in PHP?

Converting Words to Numbers in PHP: A Comprehensive Guide

Question:

Is there a straightforward way to convert numerical values expressed as words into integers in PHP?

Answer:

While there are numerous resources for converting numbers to words, finding the reverse function can be challenging. Here's a comprehensive approach that leverages a well-defined algorithm:

Steps:

1. Tokenization:

   • Split the input string into individual words called tokens.

   • Common tokens include:

     • POWER: thousand, million, billion
     • HUNDRED: hundred
     • TEN: twenty, thirty... ninety
     • UNIT: one, two, three, ... nine
     • SPECIAL: ten, eleven, twelve, ... nineteen

2. Right-to-Left Parsing:

   • Start from the rightmost token.

   • Group consecutive tokens to match patterns representing combinations of UNIT, HUNDRED, TEN, and SPECIAL tokens. For example:

     • UNIT HUNDRED TEN UNIT
     • UNIT HUNDRED UNIT
     • SPECIAL

3. Convert to Numbers:

   • Translate each pattern to its corresponding numerical value (e.g., "twenty-one" -> 21).
   • Aggregate these values to obtain the final number.

4. Iterative Processing:

   • If the right-to-left parsing reaches a POWER token, restart the process at the next highest POWER or the end of the string.
   • Continue until you reach the beginning of the string.

Example:

Consider the input string "iPhone has two hundred and thirty thousand seven hundred and eighty three apps."

• Tokenization: ["iPhone", "has", "two", "hundred", "and", "thirty", "thousand", "seven", "hundred", "and", "eighty", "three", "apps"]
• Right-to-Left Parsing:

  "three" -> 3
  "eighty" -> 80
  "and" -> (ignored)
  "seven" -> 7
  "hundred" -> 700
  "and" -> (ignored)
  "thirty" -> 30
  "thousand" -> 30000
  "two" -> 2
  "hundred" -> 200
  "and" -> (ignored)

• Convert to Numbers:

  30000 + 200 + 30 + 700 + 80 + 3 = 230783

Therefore, "iPhone has two hundred and thirty thousand seven hundred and eighty three apps" becomes "iPhone has 230783 apps."

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