v3.23.1

Subsequent event (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2023	Mar. 10, 2023	Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2020
Subsequent Event [Line Items]
Cash and cash equivalents	$ 176,683		$ 313,812	$ 218,781	$ 90,315
Third SVB Facility
Subsequent Event [Line Items]
Number of months with sufficient funds to operate (in months)	12 months
Subsequent event | Third SVB Facility
Subsequent Event [Line Items]
Cash and cash equivalents		$ 170,000
Subsequent event | Third SVB Facility | Revolving credit facility
Subsequent Event [Line Items]
Allowable cash hold outside of facility		$ 165,000

X

- Definition

Debt Instrument, Covenant, Cash Hold Outside Of Facility

+ References

No definition available.

+ Details

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Namespace Prefix:	phr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Estimated Number Of Months The Company Have Sufficient To Fund Its Operations

+ References

No definition available.

+ Details

Name:	phr_EstimatedNumberOfMonthsTheCompanyHaveSufficientToFundItsOperations
Namespace Prefix:	phr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3521-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3044-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126999549&loc=SL98516268-108586

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: